part 0.012, on the base 0.02; length of the apophyses 0.02 to 0.03.

_Habitat._--Mediterranean, Atlantic, Stations 348, 354, surface.

2. _Xiphacantha crucifera_, n. sp.

Spines slender, four-sided prismatic, thin, of nearly equal breadth throughout the whole length. Base with small wing-cross. Four apophyses much nearer the proximal than the distal end, thin, straight smooth, three to six times as long as the basal breadth of the spine. Central capsule pellucid, with yellow bodies.

_Dimensions._--Length of the spines 0.4 to 0.5, breadth 0.002 to 0.004; length of the apophyses 0.01 to 0.02.

_Habitat._--Central Pacific, Station 266, surface.

3. _Xiphacantha spinulosa_, Haeckel.

_Xiphacantha spinulosa_, Haeckel, 1862, Monogr. d. Radiol., p. 388, Taf. xvii. fig. 4.

_Acanthometra spinulosa_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 807.

Spines stout, four-sided prismatic, of nearly equal breadth throughout the whole length, on the distal apex truncated, two-edged. Base with large wing-cross. Four apophyses about in the middle of each spine, conical, straight, spinulated, twice to four times as long as the basal breadth of the spine. Central capsule opaque, yellow.

_Dimensions._--Length of the spines 0.27, breadth 0.014; length of the apophyses 0.05.

_Habitat._--Mediterranean (Messina), surface.

4. _Xiphacantha emarginata_, n. sp.

Spines stout, four-sided, in the proximal half prismatic, in the distal half pyramidal, with emarginated apex. Base with very large wing-cross. Four apophyses about in the middle of each spine, compressed, straight, two-edged, with emarginated ends, about twice as long as the basal breadth of the spine. Central capsule small, pellucid.

_Dimensions._--Length of the spines 0.2 to 0.3, breadth 0.02 to 0.03; length of the apophyses 0.04 to 0.06.

_Habitat._--South Pacific, Station 291, surface.

5. _Xiphacantha falcata_, n. sp.

Spines slender, four-sided prismatic, gradually thickened from both ends towards the middle part, with simple apex. Base with very small wing-cross. Four apophyses about in the middle part of each spine, falcated, compressed, recurved, twice to three times as long as the greatest breadth of the spine.

{760}_Dimensions._--Length of the spines 0.3 to 0.4, greatest breadth 0.015; length of the apophyses 0.03 to 0.05.

_Habitat._--Central Pacific, Station 270, surface.

6. _Xiphacantha ancorata_, n. sp.

Spines slender, four-sided prismatic, gradually thickened from the narrow base towards the short, simple, pyramidal apex. Base with large wing-cross. Four apophyses on the distal end, immediately below the pyramidal apex, falcated, strongly recurved, like an anchor with four strong teeth.

_Dimensions._--Length of the spines 0.4 to 0.5, basal breadth 0.005, distal breadth 0.015; length of the apophyses 0.04.

_Habitat._--Indian Ocean, Madagascar, Rabbe.

Subgenus 2. _Xiphacanthidium_, Haeckel.

_Definition._--Apophyses of the radial spines broad, compressed, wing-shaped, formed like a large thin plate. Edges of the spines commonly broad, strongly prominent.

7. _Xiphacantha stauroptera_, n. sp.

Spines four-winged, from the middle part little thinner towards both ends. Apex simple pyramidal. Base with small wing-cross. Four apophyses wing-shaped, isosceles triangular or truncated quadrangular; their base is about half as broad as their length, and occupies in the basal half of each spine about one-sixth to one-eighth of its length.

_Dimensions._--Length of the spines 0.1 to 0.15; greatest breadth (diagonal of the cross of the apophyses) 0.006 to 0.009.

_Habitat._--South Atlantic, Station 332, surface.

8. _Xiphacantha trigonoptera_, n. sp.

Spines four-winged, tapering rapidly from the broad middle part towards both ends. Apex simple pyramidal. Base with a small wing-cross. Four apophyses equilateral triangular; their base occupies the middle of each spine, extending to about one-fifth of its length.

_Dimensions._--Length of the spines 0.15 to 0.2, greatest breadth (diagonal of the cross of the apophyses) 0.06 to 0.08.

_Habitat._--Central Pacific, Station 272, surface.

9. _Xiphacantha macroptera_, n. sp.

Spines four-winged, from the broad middle part gradually thinner towards both ends. Apex simple pyramidal. Base with small wing-cross. Four apophyses wing-shaped, very long and broad, {761}triangular; their base occupies about the middle third of each spine; the proximal side of each wing is the shortest, truncated or concave.

_Dimensions._--Length of the spines 0.4 to 0.5, greatest breadth (diagonal of the middle leaf-cross) 0.08 to 0.12.

_Habitat._--North Pacific, Stations 253 to 256, surface.

10. _Xiphacantha platyptera_, n. sp.

Spines four-winged, nearly prismatic in the basal and distal parts. Apex truncated. Base with small wing-cross. Four apophyses wing-shaped, very broad and thin, extremely delicate, of irregular quadrangular or nearly rhomboidal form; their base occupies the middle half of the length of the spines (second and third quarter). Very variable in form. Often the edges of the wing-apophyses of the neighbouring spines seem to meet.

_Dimensions._--Length of the spines 0.2 to 0.3, greatest breadth (diagonal of the leaf-cross) 0.06 to 0.08.

_Habitat._--Pacific, widely distributed, Stations 239, 253, 272, 288, &c., surface.

11. _Xiphacantha ciliata_, n. sp. (Pl. 129, figs. 4, 5).

Spines four-winged, prismatic in the basal and the distal third. Apex pyramidal, short. Base with large leaf-cross. Four apophyses wing-shaped, nearly semicircular, with dentated edges and rough spinulate or porous faces; their base occupies the middle third of the length of each spine.

_Dimensions._--Length of the spines 0.2 to 0.3, greatest breadth (diagonal of the apophysial cross) 0.08 to 0.12.

_Habitat._--Tropical Atlantic, Stations 342 to 352, surface.

12. _Xiphacantha alata_, Haeckel.

_Xiphacantha alata_, Haeckel, 1862, Monogr. d. Radiol., p. 388.

_Acanthometra alata_, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 48, Taf. ix. figs. 1-3.

Spines four-winged, prismatic in the basal quarter, more slender in the distal half. Apex simple pyramidal. Base with small wing-cross. Four apophyses wing-shaped, nearly semicircular, with denticulated edges (and often also with spinulate faces); their base occupies the second quarter of the length of each spine.

_Dimensions._--Length of the spines 0.3 to 0.4, greatest breadth (diagonal of the apophysial cross) 0.05 to 0.06.

_Habitat._--Mediterranean (Nice), Müller, (Portofino), Haeckel.

Genus 331. _Stauracantha_,[371] Haeckel, 1881, Prodromus, p. 465.

_Definition._--#Astrolonchida# with four branched (but not latticed) apophyses on each radial spine, opposite in pairs in the form of a cross.

{762}The genus _Stauracantha_ differs from its ancestral form, _Xiphacantha_, in the ramification of the four crossed apophyses on each spine. These bear either lateral branches, which are parallel to the cross axes of the radial spine itself (subgenus _Stauracanthonium_), or they are forked, with divergent branches not parallel to those cross axes (subgenus _Stauracanthidium_). Both subgenera may perhaps be better separated as genera. They form the transition to the _Stauraspida_.

Subgenus 1. _Stauracanthonium_, Haeckel.

_Definition._--Apophyses of the radial spines not forked, but crossed by perpendicular branches, which are placed in tangential planes and parallel to the cross axes of the quadrangular spine itself.

1. _Stauracantha orthostaura_, n. sp. (Pl. 130, fig. 5).

Spines four-sided prismatic, with simple apex and small leaf-cross at the base; with four thin slender conical apophyses in the proximal third. Each apophysis represents a regular rectangular cross, being intersected in its middle by one perpendicular rod of its own length.

_Dimensions._--Length of the spines 0.3, breadth 0.02; distance of the apophyses from the apex 0.15 to 0.2.

_Habitat._--South Pacific, Station 169, surface.

2. _Stauracantha tetrastaura_, n. sp.

Spine four-winged prismatic, with four broad prominent edges, pyramidal apex, and large basal leaf-cross, with four broad compressed apophyses about in the middle. Each apophysis represents a vertical lamella (placed in a meridian) with convex distal and concave proximal edge, and is crossed in its apical part by one perpendicular short rod.

_Dimensions._--Length of the spines 0.5, breadth 0.03; distance of the apophyses from the centre 0.2.

_Habitat._--Central Pacific, Station 272, surface.

3. _Stauracantha diplostaura_, n. sp.

Spines four-sided prismatic, with truncated apex and broad basal leaf-cross; in the proximal half with four slender conical apophyses. Each apophysis is crossed in its apical half at right angles by two short parallel transverse rods.

_Dimensions._--Length of the spines 0.32, breadth 0.012; distance of the apophyses from the centre 0.11.

_Habitat._--South Pacific, Station 291, surface.

{763}4. _Stauracantha scalaris_, n. sp.

Spines four-winged prismatic, with four broad prominent edges, truncated apex, and small basal leaf-cross; in the proximal third with four compressed lamellar apophyses. Each apophysis is pinnate with opposite pinnulæ, or crossed at right angles by three to six parallel transverse rods.

_Dimensions._--Length of the spines 0.24, breadth 0.016; central distance of the apophyses 0.12.

_Habitat._--Indian Ocean (Madagascar), Rabbe, surface.

5. _Stauracantha johannis_, n. sp. (Pl. 132, fig. 11).

Spines four-sided pyramidal, with simple apex and broad basal leaf-cross, with four large conical apophyses about in their middle. Each apophysis bears two irregular rows of alternating perpendicular lateral branches, the length of which decreases from the base towards the apex of the apophysis.

_Dimensions._--Length of the spines 0.2, middle breadth 0.02; central distance of the apophyses 0.1.

_Habitat._--South-east Pacific (off Juan Fernandez), Station 300, surface.

6. _Stauracantha murrayana_, Haeckel.

_Xiphacantha species_, Wyville Thomson, 1877, The Atlantic, vol. i. p. 235, fig. 53.

_Xiphacantha murrayana_, Haeckel, 1878, Protistenreich, p. 45, fig. 33.

Spines quadrangular prismatic, with pyramidal apex and small basal leaf-cross, with four regular conical apophyses in the proximal part. Each apophysis is crossed at right angles by two parallel transverse rods; the smaller apical rod is simple; the larger basal rod is crossed again on each side by a secondary perpendicular branch, which therefore is parallel to the apophysis itself.

_Dimensions._--Length of the spines 0.3, breadth 0.01, distance of the apophyses 0.08.

_Habitat._--South Atlantic, Station 332, surface.

7. _Stauracantha pinnulata_, n. sp.

Spines four-winged pyramidal, with prominent edges, simple apex and large basal leaf-cross, in the middle with doubly pinnate triangular apophyses. Each apophysis is crossed at right angles by three to four transverse parallel rods, which bear again perpendicular secondary branches; the outline of the doubly pinnate apophysis is an isosceles triangle.

_Dimensions._--Length of the spines 0.3, middle breadth 0.02; distance of the apophyses 0.12.

_Habitat._--North Pacific, Station 244, surface.

{764}Subgenus 2. _Stauracanthidium_, Haeckel.

_Definition._--Apophyses of the radial spines forked, each with two divergent terminal branches, which are not parallel to the cross axes of the quadrangular spine.

8. _Stauracantha stauraspis_, Haeckel.

_Dorataspis polyancistra, juvenis_, Haeckel, 1862, Monogr. d. Radiol., p. 418, Taf. xxi. fig. 7.

Spines slender, quadrangular prismatic, with simple apex and pyramidal base (without basal leaf-cross); with four slender apophyses, which are simply forked in the outer third. Each apophysis with two recurved fork branches.

_Dimensions._--Length of the spines 0.12, breadth 0.004; distance of the apophyses 0.06.

_Habitat._--Mediterranean (Messina), surface.

9. _Stauracantha bifurca_, n. sp.

Spines stout, four-winged prismatic, with pyramidal apex and pyramidal base (without leaf-cross); in their middle with four compressed, little curved apophyses (convex on the outer, concave on the inner edge), which are simply forked at the end. Each apophysis with two short straight fork branches.

_Dimensions._--Length of the spines 0.2, breadth 0.006; distance of the apophyses 0.08.

_Habitat._--Central Pacific, Station 266, surface.

10. _Stauracantha quadrifurca_, n. sp. (Pl. 130, fig. 4).

Spines slender, four-sided prismatic, with simple apex and pyramidal base (without leaf-cross); with four slender apophyses, which are doubly forked about in their middle. Each apophysis with four short and thin terminal branches.

_Dimensions._--Length of the spines 0.2, breadth 0.002; distance of the apophyses from the centre 0.08.

_Habitat._--South Atlantic, Stations 325 to 330, surface.

Genus 332. _Phatnacantha_,[372] Haeckel, 1881, Prodromus, p. 465.

_Definition._--#Astrolonchida# with four apophyses on each radial spine, opposite in pairs in cross form, and forming a lattice-plate by communicating branches.

The genus _Phatnacantha_ has been derived from the preceding _Stauracantha_ by concrescence of the branches of the apophyses. Therefore each spine bears a lattice-plate or a fenestrated shield. If the growing plates of the neighbouring spines {765}meet together, then the characteristic lattice-shell of the Tessaraspida is perfect. Either each plate bears four crossed pores (like _Tessaraspis_), or a larger number of pores (four aspinal and four to eight or more coronal) like _Icosaspis_.

1. _Phatnacantha tessaraspis_, n. sp.

Spines quadrangular prismatic, with simple pyramidal apex and small basal leaf-cross. Each spine bears in the basal half a square plate, which is perforated by four square pores; margin of the plate with twelve short straight teeth.

_Dimensions._--Length of the spines 0.12, breadth 0.005.

_Habitat._--Central Pacific, Station 265, surface.

2. _Phatnacantha icosaspis_, n. sp. (Pl. 130, fig. 6).

Spines quadrangular with prominent edges; prismatic in the basal half, with a broad basal leaf-cross, pyramidal in the distal half, with a simple or truncate apex. Each spine bears in the middle part a square plate, which is perforated by eight to sixteen or more square pores (four aspinal and four to eight or more coronal); margin of the plate with twenty-four to forty-eight or more short straight irregular compressed teeth.

_Dimensions._--Length of the spines 0.18, breadth 0.008.

_Habitat._--Central Pacific, Station 273, surface.

Genus 333. _Pristacantha_,[373] n. gen.

_Definition._--#Astrolonchida# with numerous simple apophyses (eight to sixteen or more on each radial spine) which are arranged in four longitudinal rows opposite in pairs in the form of a cross.

The genus _Pristacantha_ differs from all other Stauracanthida in the multiplication of the crossed apophyses (at least eight on each spine), and exhibits therefore to them the same relation as _Astrolonche_ exhibits to the other Phractacanthida. The remarkable _Astrolonchidium serratum_ appears intermediate between both groups.

1. _Pristacantha octodon_, n. sp. (Pl. 130, fig. 9).

Spines four-sided prismatic, a little broader in the middle part than at either end, with thin prominent edges. Apex truncate or pyramidal. Base pyramidal, with a small leaf-cross. From the four edges arise in the basal half (between first and second third of the length) eight slender, conical, or triangular apophyses (two on each edge).

_Dimensions._--Length of the spines 0.4 to 0.6, breadth 0.02 to 0.04.

_Habitat._--Central Pacific, Station 271, surface.

{766}2. _Pristacantha dodecodon_, n. sp. (Pl. 130, fig. 8).

Spines four-winged, of lanceolate outline, tapering from the broader middle towards the two ends. Apex pyramidal. Base with a large leaf-cross. From the four wings arise in the basal part (between first and second third of the length) twelve triangular apophyses (three from each wing).

_Dimensions._--Length of the spines 0.3, breadth in the middle 0.03.

_Habitat._--North Pacific, Station 244, surface.

3. _Pristacantha polyodon_, n. sp. (Pl. 130, fig. 7).

Spines in the distal half four-sided prismatic, thin, with pyramidal apex; in the basal half much broader, four-winged, with a large leaf-cross on the base. From the four wings of the basal half arises a variable number of slender teeth or triangular apophyses, commonly sixteen to twenty-four, often irregular (four to six from each wing).

_Dimensions._--Length of the spines 0.3 to 0.4, breadth in the distal part 0.007 to 0.01, in the basal part 0.02 to 0.03.

_Habitat._--South Pacific (off New Zealand), Station 169, surface.

Family XXXVII. #QUADRILONCHIDA#, Haeckel (Pl. 131).

_Acanthostaurida_, Haeckel, 1881, Prodromus, p. 466.

_Definition._--ACANTHARIA with twenty radial spines of very unequal size, disposed according to the law of the Icosacantha; four equatorial spines much larger than the sixteen others. No lattice-shell.

The family #Quadrilonchida# differs from the foregoing ancestral family, the Astrolonchida, in the unequal development of the twenty radial spines. The four equatorial spines are constantly much larger, and often also of another form and shape, than the sixteen other spines; often also among these the eight tropical spines are larger and of another form than the eight polar spines. Therefore the five parallel girdles or zones of every four spines, which in the Astrolonchida are equal, are here distinctly unequal. The whole body is flattened and compressed in the direction of the spineless axis, so that the equatorial plane is larger than any other plane, laid through the centre. In consequence of this flattening the central capsule is also commonly compressed and flattened, lenticular or discoidal, rarely spherical. In the Astrolonchida the "promorph" or the "geometrical fundamental form" is constantly a square double pyramid, the axes of which are of equal length. In the Quadrilonchida it becomes a square double pyramid, the two equatorial axes of which (or the diagonals of the square) are constantly longer than all other axes.

In the simpler forms of Quadrilonchida are found only two different kinds of spines, the four larger equatorial spines being of the same size and form, and the sixteen smaller {767}spines also not differing from one another (_Acanthostaurus_, &c.). But in the majority of this family there are three different kinds: four larger equatorial spines, eight tropical spines of middle size, and eight smaller polar spines (_Belonostaurus_, &c.); the latter become sometimes rudimentary, so that only twelve spines are developed (four larger equatorial and eight smaller tropical spines). In this case the development of the flat discoidal body is much stronger in the equatorial plane than in all other planes. These discoidal or lenticular Quadrilonchida exhibit a relation to the spherical Astrolonchida similar to that which the #Discoidea# exhibit to the #Sphæroidea# among the #Sphærellaria#.

A further morphological differentation takes place in the remarkable genera _Lonchostaurus_ and _Zygostaurus_. In the former (Pl. 131, figs. 4-6) the four larger equatorial spines becomes differentiated in pairs, so that the opposite equal spines of one pair, _c_1, _c_3 (in the longitudinal or hydrotomical axis), are larger, and often also of another form, than the opposite equal spines of the other pair, _c_2, _c_4 (in the transverse or geotomical axis). The most peculiar form is the rather common _Zygostaurus_ (Pl. 131, figs. 7, 8). Here the two opposite spines of one equatorial axis (of the longitudinal axis) become very different, so that the anterior or frontal spine (_c_1) is very unequal to the posterior or caudal spine (_c_3), whereas the two opposite spines, of the other equatorial axis (of the transverse axis) remain equal (_c_2, _c_4). Therefore the fundamental forms become here "amphithect," as in the Ctenophora.

The numerous Quadrilonchida may be disposed in two different subfamilies: in the Acanthostaurida all twenty radial spines are simple, without apophyses; in the Lithopterida all twenty spines (or only one part of them) bear two opposite apophyses (or lateral transverse processes). The former correspond to the Zygacanthida, the latter to the Phractacanthida among the Astrolonchida. The two opposite apophyses are simple in _Quadrilonche_ (Pl. 133, fig. 1). In _Xiphoptera_ they are provided on their distal side with lateral branches which are parallel to the spine itself. In _Lithoptera_ the spines bear two to four parallel pairs of transverse apophyses, and these are crossed by perpendicular branches, parallel to the spine itself, so that there arise fenestrated wings or latticed plates, comparable to the sails of a wind-mill. The lattice-work of these plates lies in the same meridian plane with the radial spine itself, and is therefore not comparable to the fenestrated apophyses of _Doracantha_, of _Phatnacantha_, and of the Dorataspida; in these the lattice-plates lie in tangential planes, perpendicular to the radial spine.

The apophyses of the Lithopterida may be developed either on all twenty spines equally, or only on twelve spines (four equatorial and eight tropical, whilst the eight polar spines are simple, Pl. 131, fig. 10), or only on the four equatorial spines (whilst the sixteen others are simple, Pl. 131, fig. 9).

_The Central Capsule_ of the Quadrilonchida is rarely spherical, commonly more or {768}less compressed from both poles of the spineless axis, lenticular or discoidal, sometimes square. It is enveloped by a voluminous calymma constantly bearing coronals of "Myophrisca" (compare p. 724).

_Synopsis of the Genera of Quadrilonchida._

------------------------------------------------------------------------- I. Subfamily Acanthostaurida. All twenty spines simple, without lateral apophyses (sometimes forked, but neither branched nor latticed). ------------------------------------------------------------------------- { Eight tropical and { eight polar spines { nearly equal, 334. _Acanthostaurus_. Four equatorial spines of { equal size and form. { Eight tropical and { eight polar spines { very different, 335. _Belonostaurus_.

{ Two principal spines Four equatorial spines of { of equal size and very different size or { form, 336. _Lonchostaurus_. form (the two lateral { constantly equal). { Two principal spines { (frontal and caudal) { very different, 337. _Zyostaurus_. ------------------------------------------------------------------------- II. Subfamily Lithopterida. Either all twenty spines or a part of them provided with two opposite lateral branches or apophyses. ------------------------------------------------------------------------- Apophyses simple, neither branched nor latticed, 338. _Quadrilonche_.

Apophyses branched or pinnate, but not latticed, 339. _Xiphoptera_.

Apophyses latticed, with fenestrated network, 340. _Lithoptera_.

Subfamily 1. ACASTHOSTAURIDA, Haeckel, 1881, Prodromus, p. 466.

_Definition._--#Quadrilonchida# with simple radial spines, without apophyses.

Genus 334. _Acanthostaurus_,[374] Haeckel, 1862, Monogr. d. Radiol., p. 395.

_Definition._--#Quadrilonchida# with four equatorial spines of equal size and form, which are much larger than the sixteen other spines. Eight tropical and eight polar spines nearly equal. No apophyses.

The genus _Acanthostaurus_ is the most simple and primitive form of the Quadrilonchida, and the common ancestral genus of this family; it is at the same time its most common and widely distributed form. Some species appear in astonishing numbers in different seas. It has been derived from _Acanthometron_ by stronger development of the four equatorial spines, which are all of equal size and much larger than the sixteen others.

{769}Subgenus 1. _Acostaurus_, Haeckel.

_Definition._--All twenty spines separated, in the centre united only by the triangular faces or the meeting leaf-shaped edges of their pyramidal bases.

1. _Acanthostaurus aequatorialis_, n. sp.

Spines cylindrical, of nearly equal breadth throughout their whole length. Apex simple conical. Base with a large leaf-cross. Four equatorial spines of the same form as the sixteen others, but much longer and about three times as broad.

_Dimensions._--Length of the four major spines 0.2 to 0.25, breadth 0.008; length of the sixteen minor spines 0.01 to 0.15, breadth 0.003.

_Habitat._--Equatorial Pacific, Station 271, surface.

2. _Acanthostaurus bipennis_, n. sp.

Spines linear, sword-shaped, strongly compressed, two edged; of nearly equal breadth in their whole length. Apex bifid. Base with a small leaf-cross. Four equatorial spines of the same form as the sixteen others, but twice as long and as broad.

_Dimensions._--Length of the four major spines 0.4 to 0.5, of the sixteen minor 0.2 to 0.3; breadth of the former 0.02, of the latter 0.01.

_Habitat._--North Pacific, Station 244, surface.

3. _Acanthostaurus conacanthus_, n. sp.

Spines conical, short, gradually tapering from the thick base towards the simple apex. Base with large leaf-cross. Four equatorial spines more cylindrical, twice to three times as long and as broad as the sixteen others.

_Dimensions._--Length of the four major spines 0.15 to 0.2, of the sixteen minor 0.05 to 0.08; basal breadth of the former 0.03, of the latter 0.012.

_Habitat._--South Atlantic, Station 332, surface.

4. _Acanthostaurus purpurascens_, Haeckel.

_Acanthostaurus purpurascens_, Haeckel, 1862, Monogr. d. Radiol., p. 395, Taf. xix. figs. 1, 2.

_Acanthostaurus purpurascens_, R. Hertwig, 1879, Organism. d. Radiol., Taf. i. figs. 8, 9, Taf. iii. figs. 13, 15.

_Acanthometra purpurascens_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 809.

Spines nearly cylindrical, with four blunt (often scarcely visible) edges, tapering slightly from the central to the distal end. Apex bifid, with two short parallel teeth. Base with a broad leaf-cross. {770}Four equatorial spines one and a half times to twice as long and broad as the sixteen others. Central capsule cruciate, with four arms (enveloping the basal part of the four large spines); filled up with yellow bodies and purple granules. Calymma large, with a network of purple granules. The four main spines are constantly much larger than the sixteen others, but in variable proportion. The eight polar spines are sometimes rudimentary.

_Dimensions._--Length of the four major spines 0.3 to 0.4, of the sixteen minor 0.15 to 0.3; breadth of the former 0.012, of the later 0.008 or less.

_Habitat._--Mediterranean (Messina); Atlantic, Stations 348 to 354, surface.

5. _Acanthostaurus pallidus_, Haeckel.

_Acanthostaurus pallidus_, Haeckel, 1862, Monogr. d. Radiol., p. 396.

_Acanthometra pallida_, Claparède et Lachmann, 1858, Études sur les Infusoires, &c., p. 461, Taf. xxiv. fig. 6.

Spines four-sided prismatic, with four blunt edges, of nearly equal breadth throughout their whole length. Apex bifid. Base with a small leaf-cross. Four equatorial spines much larger than the sixteen others. Central capsule spherical, transparent, containing some yellow bodies.

_Dimensions._--Length of the four main spines 0.12 to 0.2, of the sixteen others 0.04 to 0.08; breadth of the former 0.01, of the latter 0.004.

_Habitat._--North Atlantic, west coast of Norway, Claparède; Færöe Channel, John Murray.

6. _Acanthostaurus forceps_, Haeckel.

_Acanthostaurus forceps_, Haeckel, 1862, Monogr. d. Radiol., p. 396, Taf. xix. figs. 3, 4.

_Acanthometra forceps_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 809.

Spines pincer-shaped, linear, compressed, cleft nearly throughout their whole length into two parallel thin, straight branches, which are united only at the pyramidal base and by means of a small bridge in the middle part. Four main spines twice as long and as broad as the sixteen others. Central capsule square, filled up with red pigment, and containing yellow bodies. The diagonals of the square are the two equatorial axes.

_Dimensions._--Length of the four main spines 0.1, of the sixteen others 0.05; breadth of the former 0.01, of the latter 0.005.

_Habitat._--Mediterranean (Messina); North Atlantic, Canary Islands, Station 354, surface.

7. _Acanthostaurus hastatus_, Haeckel.

_Acanthostaurus hastatus_, Haeckel, 1862, Monogr. d. Radiol., p. 397, Taf. xix. fig. 5.

_Acanthometra hastata_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 809.

Spines of very different size and form; four equatorial spines cylindrical in the basal half, spear-shaped or lanceolate in the distal half, with thin edges, little longer, but five to eight times as {771}broad as the sixteen smaller spines, which are cylindrical, of equal breadth throughout their whole length, with bifid apex. Base of all twenty spines pyramidal, without leaf-cross. Central capsule yellow, spherical, or lenticular.

_Dimensions._--Length of the four major spines 0.066, breadth in the middle 0.005, on the apex 0.008; length of the sixteen smaller spines 0.054, breadth 0.001.

_Habitat._--Mediterranean (Messina), surface.

Subgenus 2. _Staurolithium_, Haeckel, 1862, Monogr. d. Radiol., p. 401.

_Definition._--All twenty spines in the centre melted and grown together, forming one single, star-like piece of acanthin.

8. _Acanthostaurus cruciatus_, Haeckel.

_Staurolithium cruciatum_, Haeckel, 1862, Monogr. d. Radiol., p. 401, Taf. xx. fig. 6.

_Astrolithium cruciatum_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 811.

Spines cylindrical, of equal breadth throughout their whole length. Apex simple conical. Four equatorial spines twice as long and broad as the sixteen other spines. All twenty spines in the centre melted and grown together, forming a single piece of acanthin. Central capsule spherical, red-brown, opaque.

_Dimensions._--Length of the four equatorial spines 0.12, breadth 0.006; length of the sixteen smaller spines 0.06, breadth 0.003.

_Habitat._--Mediterranean (Messina), surface.

Genus 335. _Belonostaurus_,[375] n. gen.

_Definition._--#Quadrilonchida# with four equatorial spines of equal size and form, which are much larger than the sixteen other spines. Eight tropical and eight polar spines very different. No apophyses.

The genus _Belonostaurus_ differs from the preceding _Acanthostaurus_ in the unequal size and form of the eight tropical and the eight polar spines; the latter are much smaller than the former and often quite rudimentary, so that the skeleton appears composed only of twelve spines, four larger equatorial and eight smaller tropical spines. The central bases of the polar spines are constantly preserved. The central capsule is a flattened square disk.

1. _Belonostaurus quadratus_, n. sp.

Four equatorial spines little compressed, almost cylindrical in the basal half, lanceolate, broader, with simple apex in the distal half. Eight tropical spines a little shorter, but only half as broad, {772}sword-shaped, two-edged, of equal breadth, with simple apex. Eight polar spines very short, conical, also with simple apex. Base without leaf-cross, a simple pyramid.

_Dimensions._--Length of the four equatorial spines 0.18, of the eight tropical spines 0.14, of the eight polar spines 0.04.

_Habitat._--Central Pacific, Station 271, surface.

2. _Belonostaurus bicuspis_, n. sp.

Four equatorial spines compressed, almost lanceolate in the basal half, bifid, with two large, bent, little divergent horns in the distal half. Eight tropical spines nearly of the same form, but only half as large, with much smaller horns. Eight polar spines rudimentary, very short, conical, with simple apex. Base with a large leaf-cross.

_Dimensions._--Length of the four equatorial spines 0.2, of the eight tropical spines 0.1, of the eight polar spines 0.02.

_Habitat._--Central Pacific, Station 263, surface.

Genus 336. _Lonchostaurus_,[376] Haeckel, 1862, Monogr. d. Radiol., p. 397 (_sensu emendato_).

_Definition._--#Quadrilonchida# with four equatorial spines of unequal size and form; the principal spines (in the longitudinal axis) larger than the lateral spines (in the transverse axis); both opposite spines of each pair equal. Sixteen other spines much smaller (often the eight tropical larger than the eight rudimentary polar spines). No apophyses.

The genus _Lonchostaurus_ differs from the two preceding genera in the unequal size and shape of both equatorial pairs of spines, whilst the two opposite spines of each pair are equal. Therefore the equatorial plane is here a rhombus, not a square, as in the preceding genera. We encounter here for the first time the differentiation of the two equatorial axes, the longitudinal (or hydrotomical) and the transverse (or geotomical) axis. The sixteen other spines are constantly smaller (often also the eight polar more or less rudimentary).

1. _Lonchostaurus rhomboides_, n. sp. (Pl. 131, fig. 6).

Four equatorial spines cylindrical, twice to three times as broad as the sixteen smaller spines, conical at the distal apex; the two opposite spines of the longitudinal axis twice as long as those of the transverse axis. Sixteen smaller spines conical at the base, with simple bristle-shaped apex. The surface of the rhombical calymma, including the spines, was covered in the figured specimen with small plates like those of _Sphærocapsa_.

_Dimensions._--Length of the cross (longitudinal axis) 0.24, breadth (transverse axis) 0.12.

_Habitat._--South Pacific, Station 302, depth 1450 fathoms.

{773}2. _Lonchostaurus lanceolatus_, n. sp.

Four equatorial spines compressed, lanceolate, tapering equally from the middle towards the two ends; the two opposite spines of the longitudinal axis one and a half times as long as those of the transverse axis. Sixteen smaller spines compressed, linear, two-edged, half as long and only one-fourth as broad as the two longitudinal spines.

_Dimensions._--Length of the equatorial cross 0.3, breadth 0.2.

_Habitat._--Central Pacific, Station 272, surface.

3. _Lonchostaurus bifidus_, n. sp.

Four equatorial spines compressed, nearly rectangular, forked, with two long and thin, bent, little divergent horns; the two opposite spines of the longitudinal axis about one-third longer and broader than those of the transverse axis. Sixteen smaller spines of the same form, also forked, but the eight tropical only half as large, and the eight polar spines scarcely one-fourth as large as the two longitudinal spines.

_Dimensions._--Length of the equatorial cross 0.36, breadth 0.26.

_Habitat._--South-west Pacific, Station 166, surface.

4. _Lonchostaurus bifurcus_, n. sp. (Pl. 131, fig. 4).

Four equatorial spines nearly rhomboidal, about one and a half times as large as the eight tropical and three times as large as the eight polar spines; the two opposite spines of the longitudinal axis only with two large divergent straight horns; the two spines of the transverse axis somewhat shorter, with four short horns (the two outer horns longer than the two inner). Eight tropical spines doubly forked, each with four thin bristle-shaped horns. Eight polar spines very short, each with two thin bristle-shaped, much divergent horns.

_Dimensions._--Length of the equatorial cross 0.34, breadth 0.28.

_Habitat._--North-west Pacific, Station 236, surface.

5. _Lonchostaurus rhombicus_, n. sp.

Four equatorial spines nearly rhomboidal, tapering from the broader middle towards the two ends. Leaf-cross of their base very large. The two opposite spines of the longitudinal axis about one-third larger than the two spines of the transverse axis. Eight tropical spines of the same form, but only half as large. Eight polar spines rudimentary, very short, conical.

_Dimensions._--Length of the equatorial cross 0.4, breadth 0.3.

_Habitat._--North Pacific, Station 253, surface.

6. _Lonchostaurus crystallinus_, n. sp. (Pl. 131, fig. 5).

Four equatorial spines lanceolate or rhomboidal, with broad leaf-cross at the base, of a peculiar crystalline structure and a lamellated surface, both opposite spines of the longitudinal axis twice as {774}large as the two spines of the transverse axis. Eight tropical spines of similar form, but only half as large, and with a very large, extremely prominent, lamellated leaf-cross. Eight polar spines quite rudimentary, scarcely prominent.

_Dimensions._--Length 0.36, breadth 0.2.

_Habitat._--Central Pacific, Station 271, surface.

Genus 337. _Zygostaurus_,[377] n. gen.

_Definition._--#Quadrilonchida# with four equatorial spines of unequal size and form; both lateral spines (in the transverse axis) equal; but both principal spines (in the longitudinal axis) very different, the frontal larger than the caudal. Sixteen other spines much smaller (often the eight tropical larger than the eight rudimentary polar spines). No apophyses.

The genus _Zygostaurus_ differs from all other Staurolonchida in the peculiar differentiation of the four equatorial spines; the two opposite spines of the hydrotomical or longitudinal axis being very different in size and form (the frontal spine forked, the caudal spine simple); whilst the two opposite spines of the geotomical or lateral axis (perpendicular to the former) are equal, forked, but different in shape from the former. Therefore the geometrical fundamental form of the body in this remarkable genus becomes "amphithect" or "bilateral" in the widest signification of this term (comp. my General Morphology, vol. i. pp. 480, 482). Of the three different dimensive axes one (the longitudinal) exhibits unequal poles, whilst the two other (the sagittal and lateral) axes exhibit equal poles.

1. _Zygostaurus amphithectus_, n. sp. (Pl. 131, fig. 7).

Frontal spine (_c_1) little different from the two lateral spines; each with two divergent curved horns, which are equal and of about the same length as the simple broad basal part. Caudal spine (_c_3) simple, spindle-shaped, about as long as the frontal spine. Tropical spines little smaller than the three former, and of the same symmetrical forked form. Eight polar spines much smaller, but also forked, with thin bristle-shaped branches.

_Dimensions._--Length of the cross (longitudinal axis) 0.5, breadth (lateral axis) 0.4.

_Habitat._--Central Pacific, Station 272, surface.

2. _Zygostaurus longicornis_, n. sp.

Frontal spine (_c_1) little different from the two lateral spines, each with two divergent curved horns, which are equal and of about the same length as the simple broad basal part. Caudal {775}spine (_c_3) simple, lanceolate, shorter than the frontal spine. Eight tropical spines in the basal part smaller than the three former, but with much longer fork-branches, which are prolonged into very thin and long bristles. Eight polar spines rudimentary, very short.

_Dimensions._--Length of the equatorial cross 0.4, breadth 0.3.

_Habitat._--South Pacific, Station 295, surface.

3. _Zygostaurus cornutus_, n. sp.

Frontal spine (_c_1) little different from the two lateral spines, each with two divergent straight horns, which are shorter than the basal part. Caudal spine (_c_3) simple, triangular, shorter than the three former. Eight tropical spines of equal size and form, doubly forked, each with four thin, bristle-shaped, little divergent teeth. Eight polar spines short, simply forked.

_Dimensions._--Length of the equatorial cross 0.5, breadth 0.4.

_Habitat._--Indian Ocean (Madagascar), Rabbe, surface.

4. _Zygostaurus caudatus_, n. sp.

Frontal spine (_c_1) very different from the others, pincer-shaped, with two long, nearly parallel slightly bent horns. Lateral spines (_c_2 and _c_4) only half as long, with two short, nearly parallel horns. Caudal spine (_c_3) very long and stout, spindle-shaped, about twice as long as the frontal spine. Eight tropical spines of equal size and form, symmetrical, with two long and thin, divergent horns. Eight polar spines short and stout, with two divergent horns.

_Dimensions._--Length of the equatorial cross 0.8, breadth 0.3.

_Habitat._--Central Pacific, Station 265, surface.

5. _Zygostaurus frontalis_, n. sp.

Frontal spine (_c_1) very different from the others, with two very long, divergent, stout branches. Lateral spines (_c_2 and _c_4) only half as long, each with two stout, nearly parallel horns of equal length. Caudal spine (_c_3) simple, sword-like, shorter than the three former. Eight tropical spines of equal size and form, symmetrical, of the same shape as the two lateral, but only half as large. Eight polar spines very small, rudimentary, each with two short teeth.

_Dimensions._--Length of the equatorial cross 0.7, breadth 0.5.

_Habitat._--Central Pacific, Station 274, surface.

6. _Zygostaurus sagittalis_, n. sp. (Pl. 131, fig. 8).

Frontal spine (_c_1) very different from the others, with two equal, strongly divergent, bent horns. Lateral spines (_c_2 and _c_4) little smaller, but with two very unequal horns (the anterior shorter than the posterior). Caudal spine (_c_3) simple, sword-like or triangular, two-edged, longer {776}than the frontal spine. Eight tropical spines different, the four anterior (_b_1, _b_4, _d_1, _d_4) smaller, with longer horns; the four posterior (_b_2, _b_3, _d_2, _d_3) broader, with shorter horns; the anterior horn of each tropical spine is longer than the posterior. Eight polar spines rudimentary, simple, very short.

_Dimensions._--Length of the equatorial spine-cross 0.6, breadth 0.4.

_Habitat._--Central Pacific, Station 271, surface.

Subfamily 2. LITHOPTERIDA, Haeckel.

_Definition._--#Quadrilonchida# with two opposite transverse apophyses either on all twenty spines or only on a part of them.

Genus 338. _Quadrilonche_,[378] n. gen.

_Definition._--#Quadrilonchida# with two simple opposite apophyses either on each radial spine or only on a part of the twenty spines.

The genus _Quadrilonche_ is the ancestral form of the Lithopterida, or of those Quadrilonchida which bear two opposite apophyses or transverse processes. In _Quadrilonche_ these apophyses are simple, whilst they are branched in _Xiphoptera_ and fenestrated in _Lithoptera_. Each of these three genera may be divided into three subgenera; in the first only the four equatorial spines are provided with apophyses, in the second twelve spines (four equatorial and eight tropical), in the third subgenus all twenty spines.

Subgenus 1. _Quadriloncharium_, Haeckel.

_Definition._--Four large equatorial spines provided with transverse apophyses; sixteen other smaller spines simple, without apophyses.

1. _Quadrilonche tetrastaura_, n. sp.

Four equatorial spines very large, compressed, two-edged, each crossed in the distal third by two opposite simple apophyses. Sixteen other spines also compressed, linear, somewhat shorter than the former and only half as broad, without apophyses.

_Dimensions._--Length of the four major spines 0.12, breadth 0.02; length of the sixteen minor spines 0.08, breadth 0.01.

_Habitat._--Central Pacific, Station 266, surface.

{777}2. _Quadrilonche platystaura_, n. sp. (Pl. 131, fig. 2).

Four equatorial spines lanceolate, compressed, with two opposite triangular simple apophyses in the broadest middle part. Sixteen other spines also lanceolate, much smaller, of about half the length, but only of one-fourth the breadth, without apophyses.

_Dimensions._--Length of the four major spines 0.2, breadth 0.018; length of the sixteen minor spines 0.1, breadth 0.004.

_Habitat._--North Pacific, Station 235, surface.

Subgenus 2. _Quadrilonchidium_, Haeckel.

_Definition._--All twenty spines provided with transverse apophyses.

3. _Quadrilonche mesostaura_, n. sp. (Pl. 131, fig. 1).

Four equatorial spines almost of the some form and length as the sixteen others, but of double or triple the breadth; each spine in its middle third with two opposite broad triangular apophyses, in the basal third rectangular, compressed, in the distal third isosceles triangular, with simple apex.

_Dimensions._--Length of the four major spines 0.16, breadth 0.01 to 0.015; length of the sixteen minor spines 0.12, breadth 0.005.

_Habitat._--Tropical Atlantic, Station 345, surface.

4. _Quadrilonche telostaura_, n. sp.

Four equatorial spines one and a half times as long and three times as broad as the sixteen others; all twenty spines cylindrical, of equal breadth throughout their whole length, with simple conical apex; each spine crossed in the distal third by two opposite, simple, conical apophyses.

_Dimensions._--Length of the four major spines 0.3, breadth 0.012; length of the sixteen minor spines 0.2, breadth 0.004.

_Habitat._--South Atlantic, Station 325, surface.

Genus 339. _Xiphoptera_,[379] Haeckel, 1881, Prodromus, p. 466.

_Definition._--#Quadrilonchida# with two opposite branched (but not latticed) apophyses, either on each radial spine or only on a part of the twenty spines.

The genus _Xiphoptera_ differs from the preceding ancestral genus _Quadrilonche_ in the ramification of the apophyses, which bear perpendicular branches on their distal side. These are therefore parallel to the spine itself. If the branches become united by transverse beams then we get _Lithoptera_.

{778}1. _Xiphoptera tessaractena_, n. sp.

Four equatorial spines in the outer third crossed by two opposite transverse apophyses, each of which bears on its distal side two to three branches, perpendicular to the apophysis and parallel to the spine itself. Sixteen other spines much smaller, in the outer third crossed by two simple opposite transverse apophyses.

_Dimensions._--Length of the four major spines 0.18, of the sixteen minor 0.05 to 0.1.

_Habitat._--North Pacific, Station 238, surface.

2. _Xiphoptera dodecactena_, n. sp. (Pl. 131, fig. 3).

Four equatorial spines one and a half times to twice as long and broad as the eight tropical spines. These twelve spines have the same form and are crossed in their distal third by two large opposite transverse apophyses, each of which bears on its distal side two to four branches, perpendicular to the apophysis and parallel to the spine. Eight polar spines much smaller than the twelve others, simple, without apophyses. The central capsule of this species exhibited a conical protuberance around the base of each individual spine.

_Dimensions._--Length of the twelve larger spines 0.1 to 0.2, of the eight smaller 0.02 to 0.06.

_Habitat._--Central Pacific, Station 272, surface.

3. _Xiphoptera icosactena_, n. sp.

Four equatorial spines about twice as long and four times as broad as the sixteen other spines. All twenty spines crossed in the outer third by two large opposite transverse apophyses, each of which bears on its distal side two to four branches perpendicular to the apophysis and parallel to the spine itself.

_Dimensions._--Length of the four equatorial spines 0.26, of the sixteen smaller 0.11 to 0.14.

_Habitat._--South Pacific, Station 288, surface.

Genus 340. _Lithoptera_,[380] J. Müller, 1858, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 155.

_Definition._--#Quadrilonchida# with two opposite branched and latticed apophyses, either on each radial spine or only on a part of the twenty spines.

The genus _Lithoptera_, founded by Johannes Müller in 1858 for the first observed Mediterranean species, _Lithoptera fenestrata_, differs from all other Quadrilonchida in the fenestrated form of the apophyses, which he compared to the sails of a windmill. This peculiar fenestration is effected by two to four parallel pairs of opposite apophyses, which are crossed by perpendicular branches, parallel to the spine itself. {779}Therefore the wings or lattice-plates have quadrangular meshes and lie in one meridian plane of the spine, not in a tangential plane (as in the _Acanthophracta_). Commonly the lateral ends of the four broad equatorial wings are so crossed that one lateral corner of each wing lies on the upper, the other corner on the under side of both its neighbours; but sometimes the meeting corners have grown together.

Subgenus 1. _Lithopteranna_, Haeckel.

_Definition._--Four equatorial spines with transverse apophyses; sixteen others (eight tropical and eight polar spines) simple, without apophyses.

1. _Lithoptera tetraptera_, n. sp. (Pl. 131, fig. 9).

Four equatorial spines spindle-shaped, with latticed apophyses, each crossed by two transverse beams which are connected at equal distances by four rods parallel to the spine (therefore each wing with four square meshes in a single row). Lateral corners of the neighbouring wings not meeting. Sixteen smaller spines (eight tropical and eight polar) simple, conical, without apophyses.

_Dimensions._--Diagonal of the square body 0.24; length of the inner square 0.16.

_Habitat._--Tropical Atlantic, Station 348, surface.

2. _Lithoptera mülleri_, Haeckel.

_Lithoptera mülleri_, Haeckel, 1862, Monogr. d. Radiol., p. 398, Taf. xx. figs. 1, 2.

Four equatorial spines four-edged, with large latticed apophyses, each crossed by three transverse beams, which are connected at irregular distances by eight to twelve rods parallel to the spine (therefore each wing with two rows of rectangular meshes). The wings are placed not perfectly in the equatorial plane, but a little obliquely, so that each wing lies with one lateral corner on the upper, with the other corner on the under side of its neighbours. Sixteen smaller spines simple, thin, cylindrical, without apophyses.

_Dimensions._--Diagonal of the square body 0.3; length of the inner square 0.17.

_Habitat._--Mediterranean (Messina), surface.

3. _Lithoptera lamarckii_, n. sp.

Four equatorial spines four-edged, with large latticed apophyses; each crossed by three transverse beams, which are connected at short distances by twelve to sixteen rods parallel to the spine (therefore each wing with two rows of hexagonal or nearly elliptical meshes). Wings placed as in _Lithoptera mülleri_. Sixteen smaller spines simple, thin, prismatic, without apophyses.

_Dimensions._--Diagonal of the square body 0.35; length of the inner square 0.2.

_Habitat._--Central Pacific, Station 271, surface.

{780}4. _Lithoptera tetragona_, n. sp.

Four equatorial spines compressed, four-edged, with large latticed apophyses, each crossed by four transverse beams, which are connected at regular distances by eight to twelve rods parallel to the spine. (Therefore each wing with three rows of square meshes.) Wings placed in the equatorial plane and grown together by their meeting lateral ends, forming a square equatorial girdle of lattice-work. Sixteen smaller spines simple, thin, prismatic, without apophyses.

_Dimensions._--Diameter of the square body 0.4; length of the inner square 0.22.

_Habitat._--North Pacific, Station 244, surface.

Subgenus 2. _Lithopterella_, Haeckel.

_Definition._--Twelve spines (four equatorial and eight tropical) with transverse apophyses; the eight polar spines simple, without apophyses.

5. _Lithoptera quadrata_, n. sp. (Pl. 131, fig. 10).

Twelve spines with transverse apophyses; eight (polar) spines simple, small, without apophyses. Four equatorial spines very large and stout, compressed, each crossed by four transverse beams, which are connected by eight to ten rods parallel to the spine (therefore each wing with three rows of irregular rectangular meshes). Wings placed in the equatorial plane and grown together by their meeting lateral ends, forming a square equatorial girdle of lattice-work. Eight tropical spines thin, crossed by a long and thin transverse beam, which bears on its distal side eight to ten rods parallel to the spine.

_Dimensions._--Diagonal of the square body 0.35; length of the inner square 0.18.

_Habitat._--South Atlantic, Station 326, surface.

6. _Lithoptera dodecaptera_, n. sp.

Twelve spines with transverse apophyses; eight (polar) spines simple, small, without apophyses. Four equatorial spines very large, quadrangular; each crossed by three transverse beams, which are connected by ten to twelve rods parallel to the spine (therefore each wing with two rows of square meshes). Wings placed as in _Lithoptera mülleri_. Eight tropical spines much thinner, crossed each by two transverse beams, which are connected by six to eight rods parallel to the spine (therefore each wing with one row of rectangular meshes).

_Dimensions._--Diagonal of the square body 0.4; length of the inner square 0.25.

_Habitat._--Central Pacific, Station 271, surface.

Subgenus 3. _Lithopteromma_, Haeckel.

_Definition._--All twenty spines with transverse apophyses.

{781}7. _Lithoptera darwinii_, Haeckel.

_Lithoptera darwinii_, Haeckel, 1879, Natürl. Schöpfungsgesch., Aufl. vii. p. 706, Taf. xvi. fig. 12.

All twenty spines with transverse apophyses; these are quite simple in the eight small cross-shaped polar spines; also simple, but bearing some perpendicular rods, in the eight thin tropical spines. Four equatorial spines very large and stout, each crossed by four transverse beams, which are connected by eight to ten rods parallel to the spine (therefore each wing with three rows of irregular rectangular meshes). Wings placed in the equatorial plane and grown partly together by their meeting lateral ends.

_Dimensions._--Diagonal of the square body 0.4; length of the inner square 0.2.

_Habitat._--South-east Pacific, west coast of Patagonia, Station 302, surface.

8. _Lithoptera icosaptera_, n. sp.

All twenty spines with transverse apophyses, bearing one to three rows of rectangular meshes; eight polar spines small, each with a single row; eight tropical spines long and thin, each with two parallel rows. Four equatorial spines much larger and thicker, each with three parallel transverse rows of meshes. All twenty wings free, not grown together by their lateral ends.

_Dimensions._--Diagonal of the square body 0.48; length of the inner square 0.24.

_Habitat._--Indian Ocean, Belligemma, Ceylon (Haeckel), surface.

9. _Lithoptera fenestrata_, J. Müller.

_Lithoptera fenestrata_, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 154, Taf. xi. fig. 13.

All twenty spines with transverse apophyses, bearing one to three rows of irregular, rectangular meshes; eight polar and eight tropical spines small, each with a single row of meshes (between two parallel transverse beams). Four equatorial spines little larger, each with two rows (between three parallel transverse beams). Central capsule filled up with green pigment.

_Dimensions._--Diagonal of the square body 0.3; length of the inner square 0.2.

_Habitat._--Mediterranean (Saint Tropez, Nice).

Family XXXVIII. #AMPHILONCHIDA#, Haeckel (Pl. 132).

_Acantholonchida_ (Amphilonchida et Amphilithida), Haeckel, 1881, Prodromus, p. 466.

_Definition._--ACANTHARIA with twenty radial spines of very unequal size, disposed according to the law of the Icosacantha; two opposite equatorial spines (in the longitudinal axis) much larger than the eighteen others. No lattice-shell.

The family #Amphilonchida# is distinguished from all other #Acanthometra# by the excessive development of two opposite equatorial spines, which are much larger {782}than the eighteen other spines. In my Monograph (1862, p. 389) I had united all these Acanthonida in a single genus _Amphilonche_ (with ten species). Some species of it are very common and widely distributed; but in general the number of different forms in this family is much smaller than in the two foregoing families.

The two principal spines, which in all Amphilonchida are much larger than the eighteen other spines, characterise the "hydrotomical axis" or the larger equatorial axis. The two other equatorial spines or the "geotomical spines" are much smaller, and commonly of the same size as the eight tropical and the eight polar spines. In the genera _Amphilonche_ and _Amphibelone_ these eighteen smaller spines are rather equally developed; sometimes they are very small or quite rudimentary, so that the skeleton seems to be represented only by the two very long principal spines (Pl. 132, fig. 4). The genus _Acantholonche_ is distinguished by the unequal size of the eight tropical and the eight polar spines, the latter being more or less rudimentary. However, the central bases of all twenty spines, by which they are united in the centre, are constantly present. The genus _Amphibelone_ is distinguished by the unequal size and form of the two principal spines, one of them the "caudal spine," being larger (and often of another form) than the opposite "frontal spine."

The form of the radial spines is in the Amphilonchida far less varied and complicated than in the other Acanthonida (the Astrolonchida and Quadrilonchida). Apophyses or lateral transverse processes are never developed. The three main forms of spines are the same as in the other Acanthonida; they are (1) either cylindrical or conical (like _Acanthometron_), or (2) compressed or two-edged (like _Zygacantha_), or (3) quadrangular or four-edged (like _Acanthonia_). Often the spines are angular in the inner or proximal, roundish in the outer or distal part. The distal apex is commonly simple, conical or pyramidal. The central base is commonly also pyramidal, as in the majority of the Acanthonida; and the triangular faces of the neighbouring bases are simply propped one upon another. More rarely a basal leaf-cross is developed above the basal pyramid. Very rarely the central bases of the united spines grow together in the centre, so that the whole skeleton forms a single piece of acanthin.

_The Central Capsule_ is rarely spherical, commonly prolonged in the direction of the hydrotomical axis; ellipsoidal or cylindrical, sometimes also four-sided prismatic; it commonly envelops the greater part of the two principal spines; its structure and contents are the same as in the other Acanthonida.

_Synopsis of the Genera of Amphilonchida._

{ Two opposite large { principal spines Eighteen smaller spines { (frontal and caudal) of nearly equal size { equal, 341. _Amphilonche_. and similar form. { { Caudal spine larger than { the frontal spine, 342. _Amphibelone_.

Eight tropical and eight polar spines of different sizes (the latter often rudimentary), 343. _Acantholonche_.

{783}Genus 341. _Amphilonche_,[381] Haeckel, 1862, Monogr. d. Radiol., p. 389.

_Definition._--#Amphilonchida# with two equal principal spines (frontal and caudal spines not different); the eighteen smaller spines nearly equal.

The genus _Amphilonche_ represents the original and at the same time the most common form of Amphilonchida; the two opposite principal spines are of equal size and form, much larger (and often also of another form) than the eighteen smaller spines; these latter exhibit no marked differences in size and form.

Subgenus 1. _Amphiloncharium_, Haeckel.

_Definition._--Spines in the centre united by triangular faces of their pyramidal bases, propped one upon another. No basal leaf-cross.

1. _Amphilonche belonoides_, Haeckel.

_Amphilonche belonoides_, Haeckel, 1862, Monogr. d. Radiol., p. 392, Taf. xvi. fig. 6, Taf. xviii. fig. 21.

_Acanthometra belonoides_, Haeckel, 1860, Monatsber. d. k. Akad. d. Wiss. Berlin, p. 808.

Two principal spines cylindrical, of equal breadth throughout their whole length, with simple conical apex; base a small pyramid, without leaf-cross. Eighteen smaller spines conical, much shorter, with simple bristle-shaped apex. Central capsule spindle-shaped or cylindrical, yellow.

_Dimensions._--Length of the two major spines 0.4 to 0.8, of the eighteen minor 0.05 to 0.2.

_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, surface.

2. _Amphilonche lanceolata_, n. sp. (Pl. 132, fig. 1).

Two principal spines compressed, lanceolate, two-edged, gradually tapering from the broader middle towards the two ends; apex simple; base a large pyramid, with broad leaf-cross. Eighteen smaller spines about half as long, pyramidal, with simple conical or bristle-shaped apex. Central capsule lentelliptical, pink, opaque.

_Dimensions._--Length of the two major spines 0.2, of the eighteen minor 0.1.

_Habitat._--Tropical Atlantic, Station 343, surface.

3. _Amphilonche diodon_, n. sp. (Pl. 132, fig. 3).

Two principal spines compressed, lanceolate, two-edged, tapering from the broader middle towards the two ends; apex simple; base a small pyramid, without leaf-cross. Eighteen smaller spines {784}sword-shaped, only two-thirds or one-half as long, and one-third or one-fourth as broad, each with two opposite teeth in the distal part. Central capsule ellipsoidal.

_Dimensions._--Length of the two major spines 0.13, breadth 0.02; length of the eighteen minor spines 0.1.

_Habitat._--North Atlantic, Station 352, surface.

4. _Amphilonche tenuis_, Haeckel.

_Amphilonche tenuis_, Haeckel, 1862, Monogr. d. Radiol., p. 389, Taf. xvi. fig. 1, Taf. xviii. fig. 16.

_Acanthometra tenuis_, Haeckel, 1860, Monatsber. d. k. Akad. d. Wiss. Berlin, p. 807.

Two principal spines quadrangular prismatic, with smooth edges, slightly or not at all prominent, of equal breadth throughout their whole length; apex simple or bifid; base a small pyramid, without leaf-cross. Eighteen smaller spines of the same form, but only one-fourth or one-third as long. Central capsule spherical or ellipsoidal, colourless.

_Dimensions._--Length of the two major spines 0.2 to 0.3, of the eighteen minor spines 0.05 to 0.1.

_Habitat._--Mediterranean (Messina); Atlantic, Station 354, Canary Islands, surface.

5. _Amphilonche denticulata_, Haeckel.

_Amphilonche denticulata_, Haeckel, 1862, Monogr. d. Radiol., p. 390, Taf. xvi. fig. 2, Taf. xviii. fig. 17.

Two principal spines quadrangular prismatic, with prominent, elegantly denticulated edges, of equal breadth throughout their whole length; apex simple or truncated; base a small pyramid, without leaf-cross. Eighteen smaller spines of the same form, but only one-fourth or one-third as long. Central capsule ellipsoidal, opaque, yellowish-brown.

_Dimensions._--Length of the two major spines 0.3 to 0.4, of the eighteen minor 0.1; breadth of the former 0.009, of the latter 0.006.

_Habitat._--Mediterranean (Messina), Haeckel, surface.

6. _Amphilonche heteracantha_, Haeckel.

_Amphilonche heteracantha_, Haeckel, 1862, Monogr. d. Radiol., p. 293, Taf. xvi. fig. 7.

_Acanthometra heteracantha_, Haeckel, 1860, Monatsber. d. k. Akad. d. Wiss. Berlin, p. 808.

Two principal spines quadrangular prismatic, very large, with four broad, prominent, lamellar edges, of equal breadth throughout their whole length. Apex as well as the base a four-sided pyramid. Eighteen smaller spines very thin, conical, with bristle-shaped apex; base a small pyramid, without leaf-cross. Central capsule cylindrical or violin-shaped, opaque yellow.

_Dimensions._--Length of the two major spines 0.2 to 0.3, breadth 0.015 to 0.02; length of the eighteen minor spines 0.1 to 0.15, basal breadth 0.004 to 0.008.

_Habitat._--Mediterranean (Messina); Central Pacific, Station 271, surface.

{785}7. _Amphilonche elongata_, Haeckel.

_Amphilonche elongata_, Haeckel, 1862, Monogr. d. Radiol., p. 392, Taf. xviii. figs. 22_a_, 22_b_.

_Acanthometra elongata_, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 48, Taf. vii. fig. 13.

Two principal spines quadrangular prismatic in the proximal half, cylindrical or spindle-shaped in the distal half, with simple apex; base a small pyramid, without leaf-cross. Eighteen smaller spines very thin, bristle-shaped, conical on the base, with small pyramid. Central capsule spindle-shaped, transparent, yellow.

_Dimensions._--Length of the two major spines 0.3 to 0.5, breadth 0.01 to 0.03; length of the eighteen smaller spines 0.05 to 0.3.

_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific, surface.

Subgenus 2. _Amphilonchidium_, Haeckel.

_Definition._--Spines at the central base with a broad leaf-cross, composed of four prominent triangular lamellæ; between the meeting edges of the latter twenty-two pyramidal compartments or basal funnels.

8. _Amphilonche ovata_, Haeckel.

_Amphilonche ovata_, Haeckel, 1862, Monogr. d. Radiol., p. 390.

_Acanthometra ovata_, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 47, Taf. vii. fig. 10, Taf. ix. fig. 4.

Two principal spines cylindrical, of equal breadth throughout their whole length, with simple conical or bifid apex; base with a large leaf-cross of double the breadth. Eighteen smaller spines of the same form, but thinner and only half as long. Central capsule ellipsoidal, brown, opaque.

_Dimensions._--Length of the two major spines 0.3 to 0.4, breadth 0.008 to 0.012; length of the eighteen minor spines 0.1 to 0.2.

_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, surface.

9. _Amphilonche conica_, n. sp. (Pl. 132, fig. 6).

Two principal spines conical, elongate, with simple apex; base thickened, with large leaf-cross. Eighteen smaller spines also conical, of about the same basal breadth, but only one-fourth to one-half as long. Central capsule ellipsoidal, pellucid.

_Dimensions._--Length of the two major spines 0.15 to 0.2, basal breadth 0.03 to 0.04; length of the eighteen minor spines 0.05 to 0.1.

_Habitat._--Central Pacific, Stations 265 to 274, surface.

{786}10. _Amphilonche lancetta_, n. sp.

Two principal spines compressed, lanceolate, two edged, gradually tapering from the broader middle towards the two ends; apex simple; base of double the breadth, with a large leaf-cross. Eighteen smaller spines of the same form, but shorter and only half as broad. Central capsule lentelliptical, pellucid.

_Dimensions._--Length of the two major spines 0.2 to 0.3, breadth in the middle part 0.02 to 0.03; length of the eighteen smaller spines 0.1 to 0.2.

_Habitat._--South Pacific, Station 288, surface.

11. _Amphilonche complanata_, Haeckel.

_Amphilonche complanata_, Haeckel, 1862, Monogr. d. Radiol., p. 390, Taf. xvi. fig. 3, Taf. xviii. fig. 18, _a_, _b_.

_Acanthometra complanata_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 808.

Two principal spines compressed, two-edged, linear, of equal breadth throughout their whole length; apex emarginate or bifid; base with a large leaf-cross of double the breadth. Eighteen smaller spines of the same form, but only one-fourth to one-half as large. Central capsule ellipsoidal, yellow, pellucid.

_Dimensions._--Length of the two major spines 0.15 to 0.25, breadth 0.004 to 0.006; length of the eighteen minor spines 0.05 to 0.1.

_Habitat._--Mediterranean (Messina), surface.

12. _Amphilonche messanensis_, Haeckel.

_Amphilonche messanensis_, Haeckel, 1862, Monogr. d. Radiol., p. 391, Taf. xvi. fig. 4, Taf. xviii. fig. 19.

_Acanthometra messanensis_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 808.

Two principal spines quadrangular prismatic, often a little compressed from two sides, of nearly equal breadth throughout their whole length; apex either truncate or emarginate, with two opposite teeth; base with a large leaf-cross of double the breadth. Eighteen smaller spines of similar form or more compressed, much shorter. Central capsule spherical or ellipsoidal, yellow, transparent.

_Dimensions._--Length of the two major spines 0.12 to 0.18, breadth 0.016; length of the minor spines 0.05 to 0.09.

_Habitat._--Mediterranean (Messina, Corfu), Haeckel, surface.

13. _Amphilonche hydrotomica_, n. sp. (Pl. 132, fig. 2).

Two principal spines quadrangular prismatic, with four broad prominent lamellar edges or wings, of equal breadth throughout their whole length; apex pyramidal; base with a large leaf-cross. Eighteen smaller spines cylindrical or bristle-shaped, only half as long and very thin. Central capsule cylindrical or spindle-shaped, very long, opaque.

{787}_Dimensions._--Length of the two major spines 0.1 to 0.2, breadth 0.02 to 0.03; length of the eighteen minor spines 0.05 to 0.1.

_Habitat._--Central Pacific, Stations 270 to 274, surface.

14. _Amphilonche violina_, n. sp. (Pl. 132, fig. 5).

Two principal spines quadrangular prismatic, nearly violin-shaped, with four very broad, prominent, lamellar wings, which are constricted in the middle part, and broadened towards the two ends; apex truncate pyramidal; base with a large leaf-cross. Eighteen smaller spines much shorter, of equal breadth at the base, assuming the form of a quadrangular pyramid, thin prismatic in the distal half. Central capsule spindle-shaped, opaque.

_Dimensions._--Length of the two major spines 0.15 to 0.18, breadth 0.02 to 0.025; length of the eighteen minor spines 0.04 to 0.08.

_Habitat._--Central Pacific, Station 271, surface.

15. _Amphilonche tetraptera_, Haeckel.

_Amphilonche tetraptera_, Haeckel, 1862, Monogr. d. Radiol., p. 391, Taf. xvi. fig. 5, Taf. xviii. fig. 20.

_Acanthometra tetraptera_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 808.

Two principal spines four-sided pyramidal, with four broad lamellar prominent edges; apex simple or bifid; base with a large leaf-cross. Eighteen smaller spines of similar form, but only half as large. Central capsule spherical, opaque.

_Dimensions._--Length of the two major spines 0.2, breadth on the base 0.025; length of the eighteen minor spines 0.1.

_Habitat._--Mediterranean (Messina); North Atlantic, Canary Islands, Stations 352 to 354, surface.

Subgenus 3. _Amphilithium_, Haeckel, 1881, Prodromus, p. 466.

_Definition._--Spines in the basal part grown together, so that the whole skeleton represents a single piece of acanthin; a star with two larger and eighteen smaller rays.

16. _Amphilonche concreta_, n. sp. (Pl. 132, figs. 4, 4_a_).

Two principal spines cylindrical, very long, of equal breadth throughout their whole length, with simple conical apex. Eighteen smaller spines short, conical or bristle-shaped, scarcely one-fourth or one-tenth as long, often quite rudimentary. All twenty spines perfectly grown together in the centre, forming a single piece of acanthin (derived from _Amphilonche belonoides_ by central concrescence; often the sutures of the concreted bases are visible, fig. 4_a_).

_Dimensions._--Length of the two major spines 0.1 to 0.4, breadth 0.005 to 0.015; length of the eighteen minor spines 0.005 to 0.15.

_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, surface.

{788}17. _Amphilonche acufera_, n. sp.

Two principal spines thick, four-sided prismatic in the basal half, cylindrical or spindle-shaped in the distal half, with simple conical apex. Eighteen smaller spines shorter, thin, bristle-shaped or conical on the base. All twenty spines in the centre perfectly grown together, forming a single piece of acanthin. (Derived from _Amphilonche elongata_ by central concrescence.)

_Dimensions._--Length of the two major spines 0.3 to 0.5, breadth 0.01 to 0.03; length of the eighteen minor spines 0.08 to 0.2.

_Habitat._--Central Pacific, Stations 266 to 274, surface.

Genus 342. _Amphibelone_,[382] Haeckel, 1862, Monogr. d. Radiol., p. 392.

_Definition._--#Amphilonchida# with two unequal principal spines (the frontal spine very different from the caudal spine); the eighteen smaller spines nearly equal.

The genus _Amphibelone_ exhibits among the Amphilonchida the same remarkable differentiation of the two principal or longitudinal spines, as _Zygostaurus_ among the Quadrilonchida; the frontal spine differs commonly from the caudal spine not only in its size, but also in its peculiar form; commonly one pole of the longitudinal axis is much more strongly developed than the other. The eighteen smaller spines are nearly equal.

Subgenus 1. _Amphibelonium_, Haeckel.

_Definition._--All twenty spines separate, but in contact in the centre and resting one against another by the triangular sides of their pyramidal bases, without a prominent basal leaf-cross.

1. _Amphibelone aciculata_, n. sp.

Two principal spines thick, without edges and wings, the frontal spine short, spindle-shaped, the caudal three to six times as long, cylindrical, both of equal breadth, with simple conical apex and simple pyramidal base, without leaf-cross. Eighteen smaller spines very thin, bristle-shaped, of the same length as the frontal spine. Central capsule cylindrical or spindle-shaped, enveloping the two principal spines nearly throughout their whole length.

_Dimensions._--Length of the frontal spine 0.2 to 0.4, of the caudal spine 1.0 to 2.0; breadth of both 0.01; length of the eighteen smaller spines 0.1 to 0.3.

_Habitat._--South Atlantic, Station 325, surface.

{789}2. _Amphibelone cultellata_, n. sp. (Pl. 132, fig. 10).

Two principal spines broad, two-edged, knife-shaped; two opposite in the equatorial plane, thin and broad wings or lamellæ are developed, and these enclose the proximal part of both spines, whilst their distal part is free, cylindrical, with conical apex: the two wings of the longer caudal spine are lanceolate, twice to four times as broad as the two wings of the shorter frontal spine; their base is a simple pyramid without leaf-cross. Eighteen smaller spines conical, with bristle-shaped prolongation, one-fourth to one-half as long as the frontal spine. Central capsule green, semitransparent.

_Dimensions._--Length of the frontal spine 0.1 to 0.2, breadth 0.02 to 0.03; length of the caudal spine 0.2 to 0.4, breadth 0.04 to 0.08; length of the eighteen smaller spines 0.05 to 0.15.

_Habitat._--Indian Ocean, Maldive Islands (Haeckel), surface.

3. _Amphibelone pyramidata_, n. sp. (Pl. 132, fig. 9).

Two principal spines four-winged, with four crossed, very thin and broad wings, which are somewhat broader in the convex middle part than at either end; both ends of each spine four-sided pyramidal, with four concave edges and a very small terminal pyramid; base without leaf-cross. The longer caudal spine is twice as broad at the distal end as at its proximal end, and three times as broad as the distal end of the shorter frontal spine. Eighteen smaller spines bristle-shaped, with four-sided pyramidal bases. Central capsule pyramidal, enveloping the two principal spines throughout their whole length; the base of the slender quadrangular pyramid is on the caudal, the apex on the frontal pole of the longitudinal axis.

_Dimensions._--Length of the frontal spine 0.2 to 0.25, distal breadth 0.01; length of the caudal spine 0.3 to 0.4, distal breadth 0.03; length of the eighteen smaller spines 0.04 to 0.08.

_Habitat._--Cape of Good Hope, Station 143, depth 1900 fathoms.

4. _Amphibelone anomala_, Haeckel.

_Amphilonche anomala_, Haeckel, 1862, Monogr. d. Radiol., p. 394, Taf. xvi. fig. 8, Taf. xviii. figs. 23_a_, 23_b_.

_Acanthometra anomala_, Haeckel, 1860, Monatsber. d. k. Akad. d. Wiss. Berlin, p. 808.

Two principal spines four-winged, nearly prismatic, with four crossed, very broad and thick wings; both ends of each spine four-sided pyramidal, with four concave edges and a very small terminal pyramid; base without leaf-cross. The edges of the four wings are concave on the shorter frontal, convex on the longer caudal spine. Eighteen smaller spines only one-fourth to one-half as long, linear, two-edged, with two parallel teeth on the distal end. Central capsule four-sided prismatic, olive-green, enveloping almost completely the two principal spines.

_Dimensions._--Length of the frontal spine 0.12, middle breadth 0.016; length of the caudal spine 0.14, middle breadth 0.024; length of the eighteen smaller spines 0.04 to 0.06.

_Habitat._--Mediterranean (Messina), surface.

{790}Subgenus 2. _Amphibelithium_, Haeckel.

_Definition._--All twenty spines grown together in the centre, forming a single star-shaped piece of acanthin.

5. _Amphibelone clavaria_, n. sp.

Two principal spines roundish, without edges and wings; the smaller frontal spine elongate conical, the larger caudal spine two to four times as long, cylindrical, in the distal part spindle-shaped or club-shaped, with conical apex. Central base simple pyramidal, without leaf-cross. Eighteen smaller spines much shorter, bristle-shaped. Central capsule very long, club-shaped. All twenty spines perfectly grown together in the centre.

_Dimensions._--Length of the frontal spine 0.12, of the caudal spine 0.4 to 0.8; frontal breadth 0.01, caudal breadth 0.03; length of the eighteen smaller spines 0.05.

_Habitat._--Central Pacific, Station 272, surface.

Genus 343. _Acantholonche_,[383] Haeckel, 1881, Prodromus, p. 466.

_Definition._--#Amphilonchida# with two equal principal spines (frontal and caudal spines not different). The eighteen smaller spines are very unequal, ten of them (eight tropical and two transverse equatorial spines) much larger than the rudimentary eight polar spines.

The genus _Acantholonche_ differs from its ancestral genus _Amphilonche_ in the different shape of the eight tropical and the eight polar spines; these latter are much smaller than the former, which are almost equal to the two transverse equatorial spines. The two principal spines are equal, but in size and shape very different from the others.

1. _Acantholonche amphipolaris_, n. sp. (Pl. 132, fig. 7).

Two principal spines stout, quadrangular prismatic in the basal half, cylindrical or spindle-shaped in the distal half, with simple conical apex; base a small pyramid without leaf-cross. Two transverse and eight tropical spines, about half as long as the former, very thin, bristle-shaped, conical at the basal part. Eight polar spines very small, scarcely one-eighth or one-fourth as long as the latter, short pyramidal or conical, often quite rudimentary. Central capsule cylindrical, enveloping the basal half of the two principal spines.

_Dimensions._--Length of the two principal spines 0.4 to 0.5, of the ten smaller spines 0.2 to 0.3, of the eight rudimentary polar spines 0.01 to 0.06; breadth of the two large spines 0.02 to 0.03.

_Habitat._--Central Pacific, Stations 266 to 274, surface.

{791}2. _Acantholonche peripolaris_, n. sp. (Pl. 132, fig. 8).

Two principal spines quadrangular prismatic, with four broad prominent lamellar wings, of increasing breadth towards the pyramidal distal apex. Both ends of each spine four-sided pyramidal, base without leaf-cross. Two transverse and eight tropical spines about two-thirds as long as the former, four-sided pyramidal in the basal half, conical in the distal half, often curved. Eight polar spines very small, about one-fourth as long as the latter, short conical or pyramidal. Central capsule four-sided prismatic, enveloping both principal spines.

_Dimensions._--Length of the two principal spines 0.2, of the ten smaller spines 0.12, of the eight rudimentary polar spines 0.04.

_Habitat._--Central Pacific, Station 274, surface.

----

Order IV. ACANTHOPHRACTA, Richard Hertwig, 1879.

_Acanthometræ cataphractæ_, Johannes Müller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, pp. 12, 22, 49. _Dorataspida et Diploconida_, Haeckel, 1862, Monogr. d. Radiol., pp. 404, 412. _Acanthophractida_, Richard Hertwig, 1879, Organismus d. Radiol., pp. 25, 137. _Dorataspida, Diploconida, et Sphærocapsida_, Haeckel, 1881, Prodromus, p. 467.

_Definition._--ACANTHARIA with complete latticed shell.

The order #Acanthophracta#, the fourth order of Radiolaria, comprises all those ACANTHARIA in which the acanthinic skeleton is a complete latticed or fenestrated shell, supported by radial spines arising from one common central point. By the possession of such a complete shell the #Acanthophracta# differ from their ancestral group, the nearly allied #Acanthometra#, which represent the older and simpler, first order of ACANTHARIA. All #Acanthophracta# are Icosacantha (like the #Acanthonida#, their ancestral group), and possess twenty radial spines disposed according to the Müllerian law (compare above, p. 717).

Johannes Müller, who first observed five representatives of this order, called a part of them "_Acanthometræ cataphractæ_," and united these with the true #Acanthometra# (_Acanthometra costata_ and _Acanthometra cataphracta_; Abhandl. d. k. Akad. d. Wiss. Berlin, 1858, pp. 12, 49). Another part was united by him with the true _Haliomma_ (_Haliomma echinoides_, _Haliomma hystrix_, _Haliomma tabulatum_; Abhandl. d. k. Akad. d. Wiss. Berlin, 1858, pp. 36, 37). He supposed that these latter formed the immediate transition from the true #Acanthometra# to the true _Haliomma_, and that their skeleton was siliceous.

{792}In my Monograph (1862, p. 412) I founded a separate subfamily, Dorataspida, for the "_Acanthometræ cataphractæ,_" which I considered as the first subfamily of the "Ommatida." That subfamily contained at that time only two genera, _Dorataspis_ (with seven species) and _Haliommatidium_ (with five species). A third genus, _Aspidomma_ (with two species), was united by me with the Haliommatida (because of its double shell). For a fourth genus (_Diploconus_) with a single species I founded the peculiar family of Diploconida. Therefore the whole number of #Acanthophracta# described in my Monograph amounted only to four genera and fifteen species. Now the rich collections of the Challenger have added such a great number of new forms, that we may distinguish here thirty-eight genera and two hundred and twelve species.

Richard Hertwig in his excellent work (Der Organismus der Radiolarien, 1879, p. 25) separated his "Acanthophractida" perfectly from the "Ommatida" (or the siliceous #Sphæroidea#), and united them with the "Acanthometrida" in his order "Acanthometrea." But he separated them also from the nearly allied Diploconida, following my former arrangement. He distinctly noted that the skeleton in all these Acanthophractida (as well as in the Acanthometrida) consists not of silex but of the organic substance "acanthin."

The astonishing number of new and interesting forms of #Acanthophracta# which I have found in the rich collection of the Challenger enables me to distinguish now in this suborder six different families, two of which are perfectly new (the Sphærocapsida and the Hexalaspida). But the four other families also are so much enlarged that their interesting morphology appears in quite a new and clear light. Far the largest and most important of these six families is that of the true Dorataspida, which embraces seventeen genera and one hundred and eight species (more than the other five families together). From this largest and oldest ancestral family four other families have afterwards arisen, whilst a single family, the Sphærocapsida, seems to possess no direct phylogenetic connection with the five other families.

The peculiar and quite new family of Sphærocapsida (Pl. 133, figs. 7-11; Pl. 135, figs. 6-10) differs from all other #Acanthophracta# in the singular structure of the spherical acanthinic shell, composed of innumerable small plates or aglets, each of which is pierced by a very small porule. This peculiar pavemented shell (enclosing the central capsule and separated from it by the jelly-like calymma) seems to be produced on the surface of the spherical calymma, immediately by secretion of the pseudopodia, and independently from the twenty radial spines, united in the centre of the sphere. On the twenty points, where the spines perforate the shell, there are originally eighty larger pores (four around each piercing spine); but there is no certain indication that the shell is produced by the meeting apophyses of the twenty spines, as is the case in the five other families of #Acanthophracta#. Therefore perhaps it is {793}more natural to unite these latter into another suborder as #Cladophracta#, and to separate them from the Sphærocapsida, which may be called Capsophractæ.

The Dorataspida (Pls. 134-138), the common ancestral stock of the #Cladophracta#, in the definition here restricted embraces all those #Acanthophracta# in which the spherical lattice-shell is simple and composed of the meeting branches of twenty radial spines united in its centre. As already pointed out above, this family is probably diphyletic, and embraces two subfamilies which have been derived originally from two different forms of #Acanthonida#--the Diporaspida (with two opposite apophyses on each spine) derived from the Phractacanthida, and the Tessaraspida (with four crossed apophyses on each spine) derived from the Stauracanthida; in the former we find originally forty apophyses, in the latter eighty apophyses, by the meeting branches of which the spherical lattice-shell originates. The four following families of #Acanthophracta# have probably been derived from the Diporaspida.

The Phractopeltida (Pl. 133, figs. 1-6) differ from all other #Acanthophracta# in the possession of a double lattice-shell, composed of two concentric spheres which are united by the twenty radial spines meeting in the centre. As all Phractopeltida possess originally only two apophyses on each radial spine, they must be derived from the Diporaspida (_Orophaspis_), and bear to them the same relation as the Dyosphærida do to the Monosphærida. As the spherical central capsule of the Phractopeltida is enclosed between both shells, smaller than the outer, larger than the inner shell, the latter may be called "medullary shell," the former "cortical shell." This family represents among the #Acanthophracta# only the "Diplophracta," whilst all others are "Haplophracta."

The three families here characterised may be called together "#Sphærophracta#," as their central capsule and the enveloping shell are constantly spherical (or the shell sometimes an "endospherical polyhedron"). On the contrary the following three families of #Acanthophracta# may be united as "#Prunophracta#," as their central capsule and shell are never spherical, but either ellipsoidal or lenticular or of another form. The common ancestral stock of this suborder are the Belonaspida, in which the form of the central capsule and the enclosing lattice-shell is ellipsoidal; they are derived from the Dorataspida (and probably all from the subfamily Diporaspida) by the prolongation of two opposite radial spines which are larger than the eighteen others; they are the two equatorial spines of the "hydrotomical axis" (compare above, p. 719, and Pl. 136, figs. 6-9).

The Hexalaspida (Pl. 139) represent a new and very remarkable family, distinguished from all other #Acanthophracta# by the preponderating development of six stout radial spines, which are much larger than the fourteen others. These six principal spines lie in one meridian plane of the shell (in the "hydrotomical plane," p. 720), and are the two opposite equatorial spines and the four appertaining polar spines of the same plane. {794}As the fourteen smaller spines develop their apophyses at smaller distances from the centre, the shell assumes a peculiar lenticular or discoidal form, and the margin of this disk bears the six larger spines. Moreover the enclosed small central capsule is lenticular. The Hexalaspida may be derived immediately from the Belonaspida.

The Diploconida (Pl. 140) form the last and the most modified family of all #Acanthophracta#. The remarkable shell exhibits the strange form of a double cone, bearing in its axis two very large opposite spines; these are the two equatorial spines of the "hydrotomical axis" (p. 719). The double-conical or nearly cylindrical shell is composed of three different parts or segments; the small middle part is the true lattice-shell of the Hexalaspida and Belonaspida, and bears the eighteen smaller (often quite rudimentary) radial spines. The two other parts (opposite on both poles of its hydrotomical axis) are the conical or cylindrical, solid, basal sheaths of the two large equatorial spines, enveloping their major part. In consequence of this peculiar metamorphosis of the shell the Diploconida represent the last and the most aberrant group of all ACANTHARIA.

_Synopsis of the Suborders and Families of_ #Acanthophracta#.

------------------------------------------------------------------------- Suborder I. SPHÆROPHRACTA. Twenty radial spines of equal size. Shell spherical (or an endospherical polyhedron). ------------------------------------------------------------------------- Shell spherical, simple, pierced by twenty or eighty aspinal pores and composed of a pavement of innumerable very small plates or aglets, each pierced by one porule, 1. SPHÆROCAPSIDA.

Shell spherical, simple, composed of the meeting branches of two or four apophyses of the twenty radial spines, 2. DORATASPIDA.

Shell spherical, double, composed of two concentric lattice-spheres, which are connected by the twenty radial spines and composed of the meeting branches of their apophyses, 3. PHRACTOPELTIDA. ------------------------------------------------------------------------- Suborder II. PRUNOPHRACTA. Twenty radial spines of unequal size; two or six hydrotomical spines much larger than the eighteen or fourteen others. Shell not spherical. ------------------------------------------------------------------------- Shell ellipsoidal, with prolonged hydrotomical axis, the two spines of which are larger than the eighteen others, 4. BELONASPIDA.

Shell lenticular or discoidal, with six larger spines placed in the hydrotomical plane (fourteen other spines much smaller), 5. HEXALASPIDA.

Shell diploconical or nearly cylindrical, with two opposite large funnels, the sheaths of the enlarged two spines of the hydrotomical axis (eighteen other spines much smaller or rudimentary), 6. DIPLOCONIDA.

{795}----

Suborder I. SPHÆROPHRACTA, Haeckel.

_Definition._--Shell spherical, with twenty radial beams of equal size.

Family XXXIX. #SPHÆROCAPSIDA#, Haeckel (Pl. 133, figs. 7-11; Pl. 135, figs. 6-10).

_Sphærocapsida_, Haeckel, 1881, Prodromus, p. 469.

_Definition._--ACANTHARIA with simple spherical porous shell, composed of innumerable very small plates, each of which is pierced by one radial porule. Twenty radial spines of equal size meeting in the centre of the shell and disposed according to the Müllerian law of the Icosacantha, sometimes short and enclosed in the shell, at other times long and piercing it (rarely rudimentary or quite absent). Shell pierced therefore either by twenty larger perspinal pores or by eighty smaller aspinal pores. Central capsule spherical, enclosed in the porous shell.

The family #Sphærocapsida#, founded by me in 1881 for the single genus _Sphærocapsa_, represents a very peculiar and remarkable group of the #Acanthophracta#, very different from the five other families of this suborder, and probably derived, independently of them, directly from the #Acanthonida#. Whilst the lattice-shell of the five other families is composed of the meeting branches of lateral apophyses of the twenty spines, and its meshes are all or partly the intervals between these apophyses, in the Sphærocapsida the spherical shell has quite another structure, and is composed of innumerable small plates (each with one pore) which are secreted on the surface of the spherical calymma, independently of the twenty radial spines, which do not possess true apophyses.

In all Sphærocapsida the structure of the spherical shell is quite peculiar and different from that of all other Radiolaria. It is composed everywhere of innumerable very small plates or aglets, which are connected irregularly like paving-stones, and form a single continuous layer or pavement on the surface of the spherical calymma (Pl. 133, fig. 11, _a_; Pl. 135, figs. 8, 10). The small plates or paving-stones, which we will call "aglets," are connected at their meeting edges by a kind of cement, and form together with it a continuous thick capsule of acanthin. The form of the aglets is commonly more or less irregular, roundish or polygonal, sometimes longish (Pl. 133, fig. 11, _a_), more rarely it becomes rather regular, hexagonal, square, or roundish (Pl. 135, fig. 8). Usually all aglets of one and the same individual are of nearly equal size, between 0.01 and 0.02 in diameter, rarely less or more. The outer face of the aglets is more or less concave, so that the elevated meeting edges of the neighbouring aglets commonly form together a prominent network of crests (Pl. 135, figs. 8, 10); rarely the meeting edges partly cover one another like squamules (Pl. 133, fig. 11, _a_). {796}Each small plate or aglet is pierced in its centre by a single radial canalicule or porule. The dimpled surface, so produced, resembles somewhat the dimpled plates of _Ceriaspis_, &c. Different from these innumerable very small dimples of the surface are the twenty larger "spinal dimples," or the concave larger plates, which are originally pierced by the twenty radial spines. Before we describe these, we must examine the spines themselves.

The twenty radial spines of all observed Sphærocapsida (sixteen species) agree perfectly with those of the genus _Acanthonia_ (p. 749), and especially with _Acanthonia tetracopa_, _Acanthonia denticulata_, &c. All twenty spines, regularly disposed according to the Müllerian law of the Icosacantha, are of equal size, constantly four-edged prismatic, of equal breadth throughout their whole length. The prominent four edges are parallel, sometimes smooth, at other times elegantly denticulated. The central bases of the twenty spines are pyramidal, without leaf-cross, and propped one upon another with their triangular faces, as in the majority of the #Acanthonida#.

The relation of the twenty radial spines to the spherical shell exhibits in the five genera described very peculiar and important differences. In the first described genus, in _Sphærocapsa_, the spines are exactly as long as the shell-radius, and therefore are not prominent over the surface of the shell, with which they are firmly connected; the truncated distal end of the spine lies therefore here in the surface of the shell itself, and is connected with it by its four edges, between which four open aspinal pores remain, as in _Tessaraspis_, &c. (Pl. 135, figs. 6-10). In the next allied genus, _Astrocapsa_ (Pl. 133, figs. 9, 10), the spines are longer than the shell-radius, and therefore more or less prominent over its surface; the piercing part of each spine is also surrounded by four aspinal pores. In the two following genera, _Porocapsa_ and _Cannocapsa_ (Pl. 133, figs. 7, 8), the radial spines are shorter than the shell-radius and therefore quite hidden and withdrawn inside the shell, which they do not reach. But in the ideal prolongation of each spine the shell is pierced by a single large opening, the "perspinal pore" or "perspinal hole," composed of the four united aspinal pores. Whilst in _Porocapsa_ the perspinal pores are simple, they are prolonged in _Cannocapsa_ into cylindrical tubes, open at both ends. The twenty perspinal holes of these Porocapsida are therefore derived by confluence of the eighty original aspinal pores of the Astrocapsida and preserve the same regular disposition, according to the Müllerian law of the Icosacantha. Finally, the same law as is valid also in the last genus is found in _Cenocapsa_; here the radial spines have completely disappeared, and the whole skeleton is a simple sphere, but of the same structure, and with the same twenty perspinal pores as in _Porocapsa_. It is very interesting that this spineless _Cenocapsa_ among the ACANTHARIA exhibits the same shell (a simple hollow sphere) as a last reduced form, which _Cenosphæra_ among the #Sphærellaria# produces as a primitive ancestral form of numerous genera.

{797}_The Central Capsule_ of the Sphærocapsida is spherical, constantly smaller than the enclosing concentric shell, and separated from it by the calymma. Its structure seems to be the same as in the #Acanthonida#, and specially in the Astrolonchida. The pseudopodia (not yet observed) are probably protruded only through the twenty perspinal holes or the eighty aspinal pores.

_Synopsis of the Genera of Sphærocapsida._

------------------------------------------------------------------------- I. Subfamily Astrocapsida. Radial spines connected with the porous shell, as long or longer than its radius. Eighty aspinal pores. ------------------------------------------------------------------------- Spines as long as the radius, without external prolongation, 344. _Sphærocapsa_.

Spines longer than the radius, with external prolongation, 345. _Astrocapsa_. ------------------------------------------------------------------------- II. Subfamily Porocapsida. Radial spines not connected with the porous shell, shorter than its radius. Twenty perspinal pores. ------------------------------------------------------------------------- Perspinal holes of the shell simple, without external prolongation, 346. _Porocapsa_.

Perspinal holes of the shell prolonged into radial centrifugal tubuli, 347. _Cannocapsa_. ------------------------------------------------------------------------- III. Subfamily Cenocapsida. Radial spines disappeared. ------------------------------------------------------------------------- Twenty perspinal holes of the shell simple, without tubular prolongation, 348. _Cenocapsa_.

Subfamily 1. ASTROCAPSIDA, Haeckel.

_Definition._--Radial spines connected with the porous shell, as long as or longer than its radius. Therefore the shell pierced by eighty aspinal pores (four around each spine).

Genus 344. _Sphærocapsa_,[384] Haeckel, 1881, Prodromus, p. 469.

_Definition._--#Sphærocapsida# with twenty radial spines as long as the radius of the shell, without external prolongation; therefore their distal ends inserted in the perspinal holes, each of which is composed of four aspinal pores.

The genus _Sphærocapsa_ is the most common form of the Sphærocapsida, and comprises those species in which the radial spines are as long as the radius of the shell, and therefore are connected with the margin of its aspinal holes, but not prolonged beyond its surface.

{798}1. _Sphærocapsa cruciata_, n. sp. (Pl. 135, figs. 6, 7).

Aspinal holes nearly circular, with flat radially striated margin. Four aspinal pores of each hole rounded equilateral triangular. Porules of the shell simple, without ring and dimple. Four edges of the spines smooth.

_Dimensions._--Diameter of the shell 0.4 to 0.5, of the central capsule 0.3 to 0.4.

_Habitat._--North Atlantic, Færöe Channel (Gulf Stream), 1880, John Murray, surface.

2. _Sphærocapsa dentata_, n. sp. (Pl. 135, fig. 9).

Aspinal holes four-lobed, with broad concave margin denticulated on the periphery. Four aspinal pores of each hole pear-shaped, oblong, elevated in the centre. Porules of the shell simple, without ring and dimple. Four edges of the spines denticulate.

_Dimensions._--Diameter of the shell 0.3 to 0.4, of the central capsule 0.2 to 0.3.

_Habitat._--South Atlantic, Station 332, depth 2200 fathoms.

3. _Sphærocapsa quadrata_, n. sp. (Pl. 135, fig. 8).

Aspinal holes square, with concave umbilicus in the centre, surrounded by a convex denticulated margin. Four aspinal pores of each hole nearly square. Shell-porules with a polygonal elevated smooth ring, in the bottom of a shallow dimple. Four edges of the spines smooth.

_Dimensions._--Diameter of the shell 0.22, of the central capsule 0.17.

_Habitat._--Indian Ocean, south of Australia, Station 159, surface.

4. _Sphærocapsa pavimentata_, n. sp. (Pl. 135, fig. 10).

Aspinal holes four-lobed, with broad concave, irregularly crenated and figured margin. Four aspinal pores of each hole violin-shaped. Porules of the shell surrounded by an irregularly oblong ring with thick elevated, elegantly crenated margin. Four edges of the spines smooth.

_Dimensions._--Diameter of the shell 0.36, of the central capsule 0.3.

_Habitat._--South-east Pacific (off Valparaiso), Station 298, surface.

Genus 345. _Astrocapsa_,[385] n. gen.

_Definition._--#Sphærocapsida# with twenty radial spines longer than the radius of the shell, piercing its perspinal holes, with free external prolongation; therefore with four aspinal pores around each spine.

The genus _Astrocapsa_ differs from the preceding _Sphærocapsa_ in the external prolongation of the radial spines piercing the perspinal holes; it assumes therefore the common shape of the Dorataspida more than the other Sphærocapsida do.

{799}1. _Astrocapsa tritonis_, n. sp.

Aspinal holes circular, with smooth convex margin and four circular aspinal pores. Porules of the shell simple, without ring and dimple. Four edges of the spines smooth, their outer free part about as long as the diameter of the shell.

_Dimensions._--Diameter of the shell 0.25; outer length of the spines 0.3.

_Habitat._--North Atlantic, Færöe Channel, Gulf Stream (expedition of H.M.S "Triton," August, 1882), John Murray, surface.

2. _Astrocapsa stellata_, n. sp. (Pl. 133, fig. 10).

Aspinal holes cruciform, with high crenated margin. Four aspinal pores of each hole egg-shaped. Porules of the shell simple, without ring and dimple. Four edges of the spines denticulate; their outer free part twice to three times as long as the diameter of the shell.

_Dimensions._--Diameter of the shell 0.36; outer length of the spines 0.5 to 0.8.

_Habitat._--Antarctic Ocean (near Kerguelen), Station 152, surface.

3. _Astrocapsa quadrifida_, n. sp.

Aspinal holes four-lobed, with four prominent teeth between the four roundish aspinal pores. Porules of the shell surrounded by a high polygonal smooth ring. Four edges of the spines denticulate; their outer free part about as long as the radius of the shell.

_Dimensions._--Diameter of the shell 0.28; outer length of the spines 0.15.

_Habitat._--North Pacific, Station 241, surface.

4. _Astrocapsa coronata_, n. sp. (Pl. 133, fig. 9).

Aspinal holes circular, with a coronet of numerous thin parallel teeth. Porules of the shell in dimples on irregular polygonal small plates, with coronated ring. Four edges of the spines denticulate; their outer free part about twice as long as the diameter of the shell.

_Dimensions._--Diameter of the shell 0.4 to 0.5 ; outer length of the spines 1.0 to 1.2.

_Habitat._--North Atlantic, Færöe Channel, Gulf Stream (expedition of the "Knight Errant," 1880), John Murray, surface and at depths varying from 10 to 200 fathoms.

Subfamily 2. POROCAPSIDA, Haeckel.

_Definition._--Radial spines not connected with the porous shell, shorter than its radius; therefore the shell pierced by twenty perspinal pores (each one in the ideal radial prolongation of one spine).

{800}Genus 346. _Porocapsa_,[386] n. gen.

_Definition._--#Sphærocapsida# with twenty radial spines shorter than the radius of the shell; therefore their distal ends not connected with the twenty perspinal holes, which are simple, not prolonged into radial tubes.

The genus _Porocapsa_ and the following _Cannocapsa_ form together the small sub-family of Porocapsida, distinguished by the peculiar reduction or retrograde development of the twenty radial spines; all these twenty are present and disposed according to the Müllerian law of the Icosacantha, but they are shorter than the radius of the shell and therefore do not reach it. In the ideal prolongation of the spines the shell is pierced by twenty simple quadrangular or circular perspinal holes.

1. _Porocapsa murrayana_, n. sp. (Pl. 133, fig. 7).

Perspinal holes cruciform, with smooth thickened margin or with four short teeth between the four lobes. Porules of the shell simple, without ring and dimple. Four edges of the spines smooth. (Differs from _Sphærocapsa cruciata_, Pl. 135, figs. 6, 7, living in the same locality, mainly in the reduction of the radial spines, which do not reach the shell.)

_Dimensions._--Diameter of the shell 0.28; length of the spines 0.2.

_Habitat._--North Atlantic, Færöe Channel, Gulf Stream (expedition of H.M.S. "Triton," August 1882), John Murray, surface and in depths from 40 to 640 fathoms.

2. _Porocapsa tetrodon_, n. sp.

Perspinal holes cruciform, with four triangular prominent teeth between the four lobes of the cross. Porules of the shell with an elevated polygonal ring, in the bottom of a dimple. Four edges of the spines elegantly denticulate.

_Dimensions._--Diameter of the shell 0.36; length of the spines 0.12.

_Habitat._--North Pacific, Station 253, surface.

3. _Porocapsa octodon_, n. sp.

Perspinal holes square, with four larger prominent teeth on the sides of the square, and four smaller teeth on its corners. Porules of the shell surrounded by an elevated ring with elegantly crenated irregular margin. Four edges of the spines smooth.

_Dimensions._--Diameter of the shell 0.48; length of the spines 0.18.

_Habitat._--Arctic Ocean (Greenland), in the contents of the stomach of the Peromedusa, _Periphylla hyacinthina_.

{801}4. _Porocapsa coronodon_, n. sp.

Perspinal holes circular, with ciliated margin, which forms a crown of sixteen to twenty-four thin parallel teeth. Poruli of the shell surrounded by an elevated ring with high crenated margin. Four edges of the spines denticulate.

_Dimensions._--Diameter of the shell 0.55; length of the spines 0.15.

_Habitat._--Antarctic Ocean, Station 154, surface.

Genus 347. _Cannocapsa_,[387] n. gen.

_Definition._--#Sphærocapsida# with twenty radial spines shorter than the radius of the shell; therefore their distal ends not connected with the twenty perspinal holes, which are prolonged outside into radial tubes (each one in the radial ideal prolongation of one inner spine).

The genus _Cannocapsa_, exhibits the same peculiar reduction of the radial spines as the foregoing _Porocapsa_; the spines are also here shorter than the shell-radius and do not therefore reach the perspinal holes of the shell. But whilst these latter are simple in _Porocapsa_, they are prolonged into radial tubules in _Cannocapsa_; the outer surface bears therefore twenty such cylindrical tubules, separated by a short distance from the inner enclosed spines, but disposed quite regularly according to the law of Icosacantha.

1. _Cannocapsa osculata_, n. sp.

Perspinal holes prolonged into short cylindrical tubuli, the length of which about equals their diameter. Both ends of the tubuli with smooth thickened margin. Poruli of the shell simple, without ring and dimple. Four edges of the spines smooth; their length equals about four-fifths of the shell-radius.

_Dimensions._--Diameter of the shell 0.24; length of the spines 0.09, of the tubuli 0.01.

_Habitat._--North Atlantic, Færöe Channel (Gulf Stream), surface, John Murray.

2. _Cannocapsa stethoscopium_, n. sp. (Pl. 133, fig. 8).

Perspinal holes prolonged into cylindrical tubuli, half as long as the shell radius. Both ends of the tubuli with smooth thin trumpet-shaped margins. Poruli of the shell simple, without ring and dimple. Four edges of the spines smooth; their length about equals three-fourths of the shell-radius.

_Dimensions._--Diameter of the shell 0.2; length of the spines 0.08, of the tubuli 0.05.

_Habitat._--South Atlantic (west of Tristan da Cunha), Station 333, surface.

3. _Cannocapsa tubulosa_, n. sp.

Perspinal holes prolonged into cylindrical tubuli, which are as long as or longer then the shell-radius. Both ends of the tubuli with smooth thickened margin. Poruli of the shell simple, {802}without ring and dimple. Four edges of the spines smooth; their length scarcely equals half the shell-radius.

_Dimensions._--Diameter of the shell 0.15; length of the spines 0.03, of the tubuli 0.08.

_Habitat._--South Atlantic (east coast of Patagonia), Station 318, surface.

Subfamily 3. CENOCAPSIDA, Haeckel.

_Definition._--Radial spines completely reduced and absent; shell cavity therefore simple; shell pierced by twenty perspinal pores (each placed in the direction of one radial spine which has disappeared).

Genus 348. _Cenocapsa_,[388] n. gen.

_Definition._--#Sphærocapsida# without radial spines, with simple cavity of the spherical shell, which is pierced by twenty perspinal holes (each one placed in the radial direction of one spine which has disappeared).

The genus _Cenocapsa_ comprises only a single species, but is very remarkable in that it is the most reduced form among all Sphærocapsida. The twenty radial spines of the Icosacantha have perfectly disappeared by complete retrograde metamorphosis, and the only evidence of their former existence (in the ancestral genus _Porocapsa_) are the twenty perspinal holes remaining in the shell. _Cenocapsa_ is the only form of ACANTHARIA which possesses no radial spines.

1. _Cenocapsa nirvana_, n. sp. (133, fig. 11, 11_a_, 11_c_).

Perspinal holes four-lobed, cruciform, with four short triangular teeth between the four lobes of the cross. Poruli of the shell in the bottom of an elliptical dimple surrounded by an elevated ring.

_Dimensions._--Diameter of the shell 0.2 to 0.3, of the aspinal holes 0.02.

_Habitat._--North Pacific, Station 248, surface.

Family XL. #DORATASPIDA#, Haeckel (Pls. 134-138).

_Dorataspida_, Haeckel, 1862, Monogr. d. Radiol., p. 412.

_Definition._--ACANTHARIA with simple spherical lattice-shell, composed of the branched apophyses of twenty equal radial spines meeting in its centre and disposed according to the Müllerian law of Icosacantha. Central capsule spherical, enclosed in the fenestrated shell.

The family #Dorataspida# is the most important family of the #Acanthophracta#, or of those ACANTHARIA in which the radial spines are connected by a complete extracapsular lattice-shell. The Dorataspida represent probably the ancestral {803}stock of this whole order, with the exception of the Sphærocapsida. The four following families of the order may be easily derived from the Dorataspida. The number of genera (seventeen) and of species (one hundred and eight) is in this family greater than in the other five families together. When I constituted that family in my Monograph 1862, it comprised only one genus, _Dorataspis_, with seven species. The nearly allied genus _Haliommatidium_ (_Phatnaspis_) belongs to the Belonaspida.

The Dorataspida differ from the other #Acanthophracta# in the simple spherical lattice-shell, which is composed of the meeting apophyses of the twenty radial spines. In three other families of the suborder the shell is not spherical, but ellipsoidal (Belonaspida), discoidal (Hexalaspida), or diploconical (Diploconida). In the Phractopeltida the spherical shell is double, composed of two concentric lattice-spheres. In the Sphærocapsida the simple spherical shell is not composed of the apophyses of the spines, but of innumerable small plates.

The family Dorataspida may be divided into two very different subfamilies, which are probably derived, independently of one another, from two different subfamilies of the Astrolonchida. The first subfamily, Diporaspida, exhibits on each radial spine two opposite apophyses, like its ancestral group, the Phractacanthida (p. 753); whereas the second subfamily, Tessaraspida, possesses on each radial spine four crossed apophyses (opposite in pairs), like its ancestral group, the Stauracanthida (p. 758). Therefore the composition of the spherical shell, produced by the meeting branches of the tangential apophyses, is essentially different in the two subfamilies: in the Diporaspida each radial spine is surrounded by two opposite primary aspinal meshes, in the Tessaraspida by four crossed primary aspinal meshes.

Another principle of division may be established for the whole family by the different mode of composition of the shell, and regarding this important difference we may distinguish also two different subfamilies as #Cladophracta# and #Peltophracta#. In the first and simpler subfamily, the #Cladophracta#, the shell is composed totally (or sometimes partially) of the meeting branches of the apophyses of the neighbouring spines; but in each single spine (or in the most part of them) the branches of the apophyses are not united, and form no lattice-plate (Pl. 137, figs. 1 to 8). Whereas in the #Peltophracta# the shell is composed constantly of twenty perforated plates, as in each single spine the branches of its apophyses are united and form a fenestrated shield with two or four (and sometimes numerous) pores (Pls. 135, 136, 138).

In the Diporaspida as well as in the Tessaraspida we find numerous representatives of the two groups of the #Cladophracta# and of the #Peltophracta#; therefore the whole family of Dorataspida may be divided into four different tribes. The Diporaspida (with two opposite apophyses on each spine) are partly #Cladophracta# (the Phractaspida, Pl. 137, figs. 1-4), partly #Peltophracta# (the Ceriaspida, Pl. 138). On the other hand the Tessaraspida (with four crossed apophyses on each {804}spine) are also partly #Cladophracta# (the Stauraspida, Pl. 137, figs. 5-8), partly #Peltophracta# (the Lychnaspida, Pls. 135-136). The differences and relations of these tribes are placed synoptically in the following table:--

------------------------+------------------------+----------------------- | A. Diporaspida. | B. Tessaraspida. Synopsis of the four |Two opposite apophyses |Four crossed apophyses tribes of Dorataspida.| on each radial spine. | on each radial spine. | Two primary aspinal | Four primary spinal | meshes. | meshes. ------------------------+------------------------+----------------------- a. Cladophracta |1. Tribe Phractaspida. |3. Tribe Stauraspida. All twenty spines (or a | | part of them) without | | lattice-plates. | | | | b. Peltophracta |2. Tribe Ceriaspida. |4. Tribe Lychnaspida. All twenty spines with | | lattice-plates. | | ------------------------+------------------------+-----------------------

All Dorataspida are true Icosacantha, and the twenty spines, composing the spherical shell, are equally developed, regularly disposed according to the Müllerian law, and of equal size; also the distance of their plates from the common centre is equal. Nevertheless they are never of perfectly the same form; in consequence of their peculiar disposition in five zones (each with four spines) certain slight differences are effected, so that with accurate knowledge of the peculiar shell-composition it is generally not difficult to distinguish the spines of the equatorial, the two tropical, and the two polar zones.

Already the central bases, by which the twenty spines are united in the centre of the sphere, exhibit certain differences in the five zones. Commonly these bases are small pyramids, all meeting with their apex in the centre, and the triangular faces of the neighbouring pyramids are supported one upon another. The four equatorial pyramids are commonly six-sided, the other sixteen five-sided; but sometimes there are eight six-sided and twelve five-sided basal pyramids; two opposite polar spines on each pole having a six-sided base (like the four equatorial), the other two polar spines on each pole having a five-sided base (like the eight tropical). Rarely the central bases are perfectly grown together, forming a single spherical central piece of acanthin.

The three different fundamental forms of radial spines, which are found in all ACANTHARIA, the cylindrical, the two-edged, and the four-edged (spines with circular, with elliptical, and with square transverse section respectively) occur also in the different groups of Dorataspida; but commonly the two-edged or compressed form is prevalent in the Diporaspida, the four-edged or quadrangular form in the Tessaraspida. In the majority of species the spines are thickened in the shell-face, where the apophyses arise, and thinner towards the two ends. Usually the outer or distal part of the spine (outside the shell) is longer than the inner or proximal part (inside {805}the shell). The distal apex is commonly simple, conical or pyramidal, rarely bifid or truncate. The edges of the spines are commonly smooth, rarely denticulate or serrate.

The apophyses, or the lateral transverse processes of the radial spines, in the Dorataspida assume the greatest variety and complexity in form, size, mode of ramification, and in composition of the shell. An expert and practised observer may determine easily the range of each spine, whether it be an equatorial (_c_), or a tropical (_b_, _d_), or a polar spine (_a_, _e_, Pls. 133-138). The two opposite apophyses of the Diporaspida, as well as the four crossed apophyses of the Tessaraspida, lie constantly in certain meridian planes of the spine, which have a legitimate signification for each of the five zones. The comparative morphology of this regular disposition of the apophyses and the regular meeting of their branches is of the greatest interest, and necessary for the complete understanding of the complicated structure of these wonderful shells.

The pores or meshes of the spherical shell, offering the most varied forms, may generally be divided into two different groups, into sutural and parmal meshes. The sutural pores are bordered by the meeting branches of the apophyses of two, three, or four neighbouring spines, and therefore also by the sutures in which they meet. The parmal pores on the other hand are bordered only by the united branches of the apophyses of a single spine and pierce the shield or lattice-plate formed by them. Therefore the shell-meshes of the #Cladophracta# are all sutural pores (Pl. 137, figs. 1-8; rarely and only in a part of the spines parmal pores also: _Zonaspis_, _Dodecaspis_); whereas the shell-meshes of the #Peltophracta#, piercing the shields or lattice-plates of all twenty spines, are always partly sutural, partly parmal pores (Pls. 135, 136, 138). The parmal pores again may be divided into two different groups--aspinal and coronal pores. Aspinal pores ("ad spinam") are those which lie immediately on the sides of the radial spine and are bordered by the primary branches of its apophyses; therefore constantly only two in the Diporaspida, four in the Tessaraspida. Coronal pores on the contrary are those which lie in the periphery of the lattice-plates, surrounding in a circle or crown the aspinal pores and not touching the spine itself. In _Dorataspis_, _Ceriaspis_, _Tessaraspis_, _Lychnaspis_, &c., all parmal meshes are only aspinal pores (Pl. 135, figs. 2-5; Pl. 136); whilst in _Coscinaspis_, _Acontaspis_, _Icosaspis_, _Hylaspis_, &c., one part of the parmal pores is aspinal, one part coronal (Pl. 136). The number, form, and size of the coronal pores is very variable and often very large (sometimes more than a hundred in one plate).

The #Cladophracta# exhibit a comparatively simple shell-formation; either all twenty spines or at least a part of them not forming lattice-plates. The most primitive form among these is _Phractaspis_ (Pl. 137, figs. 1, 2). The forty apophyses of its twenty spines are simply forked, and their eighty fork-branches united by forty sutures, enclosing twenty-two sutural meshes: two square polar meshes (between the four polar spines on the poles of the spineless axis, _a a a a_ and _e e e e_); eight triangular {806}circumpolar meshes (each between two polar and one tropical spine, _a b a_ and _e d e_); eight quadrangular tropical meshes (each between one polar, one equatorial, and two tropical spines, _a b c b_ and _e d c d_); and four rhomboidal equatorial meshes (between two tropical and two equatorial spines, _c b c d_). If the fork-branches be again forked (_Phractaspidium_, Pl. 137, fig. 3), the number of the sutures and sutural meshes is doubled, and the same is the case in _Stauraspis_, the most simple form of the Tessaraspida.

A peculiar small group, and an interesting transition for the #Cladophracta# to the #Peltophracta#, is presented by the Zonaspida among the Tessaraspida (_Zonaspis_ and _Dodecaspis_). Here only one part of the radial spines bears lattice-plates, the other part not. In _Zonaspis_ the four equatorial spines bear lattice-plates, the sixteen other only free branches of the apophyses. In _Dodecaspis_ twelve spines are provided with lattice-plates (four equatorial and eight polar spines), whilst the eight other (tropical) spines are devoid of them.

The #Peltophracta# exhibit a great variety in the form and composition of their twenty lattice-plates or fenestrated shields. In the most simple case (a part of _Dorataspis_ and _Diporaspis_) the shell is composed of four (equatorial) hexagonal plates, and sixteen pentagonal plates (four tropical and four polar); in this case the four polar plates meet on each pole in one common point. More commonly, however, the shell seems to be composed of eight hexagonal plates (four equatorial and the four polar spines of the hydrotomical plane) and twelve pentagonal plates (eight tropical and the four polar spines of the geotomical plane); in this case only two (hexagonal) polar plates meet on each pole in a suture which separates the two other (pentagonal) polar plates (Pl. 138, fig. 4). In the majority of the Dorataspida the composition of the shell is much more complicated and often very difficult to understand. Often the surface of the plates is covered with a network of elevated crests, by which concave blind dimples are separated (_Ceriaspis_, _Hystrichaspis_, Pl. 138); and sometimes these dimples become pierced by coronal pores (Pl. 138, fig. 11, &c.).

Peculiar by-spines or "accessory spines" cover the outer surface of the shell in a great part of Dorataspida, and commonly these most characteristic by-spines are not placed radially, but parallel to the radial spine, from the lattice-plate of which they arise (Pl. 135, figs. 1, 5; Pl. 137, figs. 4-8; Monogr. d. Radiol., 1862, Taf. xxi. figs. 8, 9). They are commonly placed perpendicular to the sutural condyles, or the branch-ends of the apophyses; so that close to each suture arises a pair of divergent by-spines, belonging to the meeting apophyses of the two neighbouring spines, which meet in the suture (Pl. 137, fig. 4). Rarely these thin, bristle-shaped by-spines are quite simple and straight, commonly they undulate or are zigzag and often armed with recurved hooks. Sometimes they are also forked or arborescent (Pl. 138, fig. 7).

_The Central Capsule_ of the Dorataspida is constantly spherical and about one-third smaller than the enclosing shell, from which it is separated by the spherical calymma. {807}The membrane of the central capsule is commonly rather thin, and pierced by the twenty radial spines, meeting in the centre of the capsule. Between these lie innumerable small pores for the radiating pseudopodia; however, in many cases (and perhaps constantly) these pores exhibit a certain regular disposition. In many species the central capsule encloses Xanthellæ or symbiotic yellow unicellular Algæ. The nucleus becomes cleft very early in the majority of Dorataspida.

_Synopsis of the Genera of Dorataspida._

------------------------------------------------------------------------- I. Subfamily Diporaspida. Each radial spine with two opposite primary apophyses; therefore the whole shell with forty primary apophyses. -------------------- I. Tribe Phractaspida. Twenty radial spines without lattice-plates; no normal pores. ------------------------------------------------------------------------- No by-spines, 349. _Phractaspis_.

With by-spines, 350. _Pleuraspis_. ------------------------------------------------------------------------- II. Tribe Ceriaspida. Twenty radial spines all with lattice-plates produced by union of the branched apophyses of each plate. ------------------------------------------------------------------------- { { No by-spines, 351. _Dorataspis_. { Plates not { Forty parmal { dimpled, { With by-spines, 352. _Diporaspis_. pores (two { without { in each { network { No by-spines, but plate)--no { of crests. { free apophyses, 353. _Orophaspis_. coronal { pores in { Plates dimpled, } No by-spines, 354. _Ceriaspis_. the plates. { with a network } { of crests. } With by-spines, 355. _Hystrichaspis_.

Eighty to two hundred or more } No by-spines, 356. _Coscinaspis_. (in each plate two aspinal } and two to ten or more } With by-spines, 357. _Acontaspis_. coronal pores). } ------------------------------------------------------------------------- II. Subfamily Tessaraspida. Each radial spine with four crossed primary apophyses; therefore the whole shell with eighty primary apophyses. -------------------- III. Tribe Stauraspida. Twenty radial spines all or partly without lattice-plates. ------------------------------------------------------------------------- { No by-spines, 358. _Stauraspis_. All twenty spines without { lattice-plates. { With by-spines, 359. _Echinaspis_.

Four plates with, sixteen } without, lattice-plates. } With by-spines, 360. _Zonaspis_.

Twelve plates with, eight } without, lattice-plates. } With by-spines, 361. _Dodecaspis_. ------------------------------------------------------------------------- IV. Tribe Lychnaspida. Twenty radial spines all with lattice-plates (produced by union of the branched apophyses of each plate). ------------------------------------------------------------------------- Eighty parmal pores (four } No by-spines, 362. _Tessaraspis_. on each plate)--no coronal } pores in the plates. } With by-spines, 363. _Lychnaspis_.

One hundred and sixty to three } hundred or more parmal pores } No by-spines, 364. _Icosaspis_. (in each plate four aspinal } and four to twelve or more } With by-spines, 365. _Hylaspis_. coronal pores). }

{808}Subfamily 1. DIPORASPIDA, Haeckel.

_Definition._--#Dorataspida# with twenty radial spines, each of which bears two opposite apophyses. The spherical shell is composed either of the meeting branches of these apophyses (Phractaspida), or of twenty perforated plates, produced by concrescence of their branches (Ceriaspida).

A. Tribe I. #Phractaspida#, Haeckel.

_Definition._--#Dorataspida# without perforated plates; the spherical shell is composed only of the meeting branches of the two opposite apophyses, which arise from each radial spine. Therefore the meshes of the shell are all sutural.

Genus 349. _Phractaspis_,[389] Haeckel, 1881, Prodromus, p. 467.

_Definition._--#Dorataspida# without perforated plates; shell composed only of the meeting branches of the two opposite apophyses, which arise from each radial spine. Condyles of the branch-ends without by-spines.

The genus _Phractaspis_ is the most simple and primitive form among all Dorataspida, and may be regarded as the common ancestral form either of this whole family, or at least of its first subfamily, the Diporaspida. In all members of this subfamily the spherical shell is composed of twenty radial spines, each of which bears two opposite apophyses; but the mode of composition is different in the two tribes of the subfamily, in the Phractaspida and Ceriaspida. In the simpler tribe, the Phractaspida, the shell is composed only of the meeting branches of the apophyses of neighbouring spines; there are no peculiar perforated plates or shields. In the Ceriaspida, however, both apophyses of each single spine form a perforated plate or shield by union of their branches, and the shell is formed of the meeting edges of these shields. Of course the Ceriaspida must be derived from the simpler Phractaspida. _Phractaspis_, as the common ancestral form of both, exhibits a very simple structure of the shell (Pl. 137, figs. 1, 2). Commonly, if the fork-branches of each apophysis be not again branched, the shell possesses only twenty-two large meshes and forty sutures. More rarely their number increases, the fork-branches of the apophyses being again branched (_Phractaspidium_, Pl. 137, fig. 3).

Subgenus 1. _Phractasparium_, Haeckel.

_Definition._--Shell with twenty-two meshes, and forty sutures, each spine with only four branches, its two apophyses being simply forked.

{809}1. _Phractaspis prototypus_, n. sp. (Pl. 137, fig. 2).

Radial spines cylindrical, thin, pointed; the outer and inner halves of nearly equal size. Each spine bears in its middle part two opposite apophyses, which are simply forked; the four condyles of each spine (or the thickened ends of the fork-branches) are united with the meeting condyles of the neighbouring spines by sutures. Therefore the network of the spherical shell is composed of twenty-two large meshes: two square polar meshes on each pole (_a a a a_ and _e e e e_); eight triangular circumpolar meshes (each between two polar and one tropical spine, _a b a_ and _e d e_); eight tropical rhomboidal meshes (each between one polar, one equatorial, and two tropical spines: _a b c b_ and _e d c d_); and four rhomboidal equatorial meshes (each between two tropical and two equatorial spines _c b c d_).

_Dimensions._--Diameter of the shell 0.1, of the meshes 0.03 to 0.04; breadth of the spines and bars 0.005.

_Habitat._--Cosmopolitan; Mediterranean (Corfu), Atlantic (Stations 348, 354), Indian Ocean (Ceylon), Pacific (Stations 253, 265, 274), &c., surface.

2. _Phractaspis complanata_, n. sp. (Pl. 137, fig. 1).

Radial spines leaf-shaped, strongly compressed, two-edged, pointed; their outer part longer than the inner. Each spine with two opposite apophyses which are simply forked, therefore with four condyles. The network with forty sutures and twenty-two large meshes, as in the foregoing species. The broad faces of the eight polar spines lie in two meridian planes, of the four equatorial spines in the equatorial plane, of the eight tropical spines in two planes parallel to the latter. The planes of the leaf-shaped fork-branches lie in the spherical face.

_Dimensions._--Diameter of the shell 0.1, of the meshes 0.02 to 0.03; breadth of the fork-branches 0.012.

_Habitat._--South Atlantic, Station 343, surface.

3. _Phractaspis condylophora_, n. sp.

Radial spines quadrangular, thin; their outer pyramidal part shorter than the inner. Each spine with four branches, its two opposite apophyses being simply forked. The eighty condyles (or sutural ends of the branches) much thickened, twice to four times as broad as the branches themselves. Network with forty sutures and twenty-two large meshes, as in both foregoing species.

_Dimensions._--Diameter of the shell 0.12, of the meshes 0.03 to 0.04; breadth of the condyles 0.01.

_Habitat._--South Pacific, Station 288, surface.

4. _Phractaspis bipennis_, Haeckel.

_Dorataspis bipennis_, Haeckel, 1862, Monogr. d. Radiol., p. 413, Taf. xxi. figs. 1, 2.

_Phractasplenium bipenne_, Haeckel, 1882, Manuscript.

Radial spines very thin, quadrangular; their outer pyramidal part shorter than the inner. Each spine with four bent branches, its two opposite apophyses being simply forked. Eighty {810}condyles, very thin, pointed. In the specimens of this remarkable species, which I first observed in Messina, two opposite equatorial spines had quite free apophyses, not connected with the neighbouring spines; therefore the thin lattice-work of the shell exhibited only thirty-six sutures and twenty meshes (two meshes with six sutures, six meshes with four sutures, and twelve meshes with three sutures). In similar specimens, which I afterwards observed in the Canary Islands, all four equatorial spines were connected in the same manner with the neighbouring spines; therefore they possessed forty sutures and twenty-two meshes, like _Phractaspis prototypus_ (Pl. 137, fig. 2). Perhaps the Mediterranean species represents a peculiar genus, _Phractasplenium bipenne_.

_Dimensions._--Diameter of the shell 0.1, of the meshes 0.03 to 0.05; breadth of the spines 0.002.

_Habitat._--Mediterranean (Messina), Canary Islands (Lanzerote), surface.

Subgenus 2. _Phractaspidium_, Haeckel.

_Definition._--Shell with forty to eighty or more meshes, and eighty to one hundred or more sutures. Each spine with six to eight or more branches, its two apophyses being doubly forked or more ramified.

5. _Phractaspis constricta_, n. sp. (Pl. 137, fig. 3).

Radial spines strongly compressed, two-edged, pointed; their outer half twice constricted and somewhat longer than the inner half. Each spine with two opposite forked apophyses, the branches of which are again forked; therefore eight condyles on each spine. The network of the spherical shell with eighty sutures and sixty-two meshes (twenty-two large primary meshes and forty smaller secondary meshes, the latter between the distal fork-branches).

_Dimensions._--Diameter of the shell 0.11, of the large meshes 0.04 to 0.05, of the small meshes 0.01; breadth of the spines 0.01.

_Habitat._--South Atlantic, Station 348, depth 2450 fathoms.

6. _Phractaspis cataphracta_, Haeckel.

_Acanthometra cataphracta_, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 49, Taf. x. figs. 7, 8.

_Dorataspis cataphracta_, Haeckel, 1862, Monogr. d. Radiol., p. 415.

Radial spines thin, quadrangular; their outer pyramidal part shorter than the inner. Each spine with six to eight condyles, the fork-branches of their two opposite apophyses being (all or partly) again forked. The network with sixty to eighty sutures and meshes: sometimes as regular as in the preceding species, at other times more or less irregular.

_Dimensions._--Diameter of the shell 0.1, of the meshes 0.02 to 0.04; breadth of the bars 0.004 to 0.008.

_Habitat._--Mediterranean (Cette), Müller (Messina), Haeckel; North Atlantic, Station 353, surface.

{811}Genus 350. _Pleuraspis_,[390] Haeckel, 1881, Prodromus, p. 467.

_Definition._--#Dorataspida# without perforated plates; shell composed only of the meeting branches of the two opposite apophyses, which arise from each radial spine. Condyles of the branch ends bearing by-spines.

The genus _Pleuraspis_ has quite the same structure of the shell as the foregoing _Phractaspis_, and differs from it only in the development of external by-spines; commonly each condyle of the branch end of the apophyses bears one zigzag by-spine, which is directed parallel to the radial main-spine from which the apophyses arise. Therefore each suture of the shell is armed with two divergent by-spines (Pl. 137, fig. 4).

Subgenus 1. _Pleurasparium_, Haeckel.

_Definition._--Shell regularly developed with twenty-two meshes and forty sutures (sometimes twenty to twenty-four meshes and thirty-six to forty-eight sutures); each spine commonly with four branches, its two apophyses being simply forked.

1. _Pleuraspis horrida_, n. sp. (Pl. 137, fig. 4).

Radial spines roundish, somewhat compressed, very thick, conical, pointed at both ends, outer part nearly twice as long as the inner. Two apophyses of each spine simply forked, with short and broad branches and thickened condyles. Forty sutures, very broad. Twenty-two large meshes three to four times as broad as the bars. By-spines much developed, as long as the radius, zigzag, with alternating recurved hooks.

_Dimensions._--Diameter of the shell 0.15, of the meshes 0.04 to 0.06; breadth of the bars 0.01 to 0.015.

_Habitat._--Tropical Pacific (east of Philippines), Station 215, surface.

2. _Pleuraspis amphithecta_, n. sp.

Radial spines two-edged, leaf-shaped, strongly compressed, pointed at both ends; outer half longer than the inner. Two apophyses of each spine simply forked, with short and very broad branches; condyles not thickened. Forty sutures, broad. Twenty-two large meshes twice to three times as broad as the bars. By-spines zigzag, half as long as the radius. (Resembles _Phractaspis complanata_, Pl. 137, fig. 1.)

_Dimensions._--Diameter of the shell 0.12, of the meshes 0.02 to 0.03; bars 0.012.

_Habitat._--Central Pacific, Station 274, surface.

{812}3. _Pleuraspis costata_, Haeckel.

_Acanthometra costata_, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 49, Taf. ii. fig. 1, Taf. x. figs. 4-6.

_Dorataspis costata_, Haeckel, 1862, Monogr. d. Radiol., p. 414, Taf. xxiii. fig. 1.

Radial spines roundish, conical, pointed at both ends; outer and inner halves of nearly equal length. Two apophyses of each spine simply forked, with broad branches and thickened condyles. Forty sutures, broad. Twenty-two large meshes, four to five times as broad as the bars. By-spines straight, denticulate, half as long as the radius. (This common species is rather variable in size and details.)

_Dimensions._--Diameter of the shell 0.1 to 0.13, meshes 0.03 to 0.06, bars 0.005 to 0.01.

_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, surface.

4. _Pleuraspis pyramidalis_, n. sp.

Radial spines quadrangular, their outer part pyramidal, very thick, about half as long as the prismatic inner part. Two apophyses of each spine simply forked, with very short and broad branches. Condyles much thickened. Forty sutures, very broad. Twenty-two meshes small, the largest twice as broad as the bars; the smaller only half as broad. By-spines short, straight, denticulate, half as long as the radius.

_Dimensions._--Diameter of the shell 0.14, meshes 0.005 to 0.03.

_Habitat._--Western Tropical Pacific, Station 222, surface.

Subgenus 2. _Pleuraspidium_, Haeckel.

_Definition._--Shell with forty to eighty or more meshes and eighty to one hundred or more sutures; each spine with six to eight or more branches, its two apophyses being forked twice or oftener.

5. _Pleuraspis ramosa_, n. sp.

Radial spines roundish, stout, somewhat compressed; their inner and outer half nearly of equal length. Two apophyses of each spine doubly forked or more irregularly branched; therefore commonly eight (sometimes six, seven, nine, or ten to twelve) thickened condyles on each spine. Sutures eighty to one hundred, broad. Irregular meshes sixty to eighty; three to five times as broad as the bars. By-spines zigzag, ramified, half as long as the radius.

_Dimensions._--Diameter of the shell 0.15, of the meshes 0.007 to 0.014, breadth of the bars 0.003.

_Habitat._--Central Pacific, Station 272, surface.

{813}B. Tribe II. #Ceriaspida#, Haeckel.

_Definition._--#Dorataspida#, the spherical shell of which is composed of twenty perforated plates, produced by union of the branches of the two opposite apophyses, which arise from each radial spine. Therefore the meshes of the shell are partly sutural, partly parmal.

Genus 351. _Dorataspis_,[391] Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 811.

_Definition._--#Dorataspida# with twenty plates, which are perforated by forty aspinal pores (two pores in each plate). Surface of the shell without combs, dimples, and by-spines.

The genus _Dorataspis_ opens the long series of the Ceriaspida, or of those Dorataspida in which the shell is composed of twenty plates, each of which is perforated by two primary aspinal pores. This tribe has arisen from the simpler Phractaspida by reunion of the branches of the apophyses in each single spine. If in _Phractaspis_, their common ancestral form (Pl. 137, figs. 1, 2), the neighbouring fork-branches of both opposite apophyses in each radial spine become recurved and united, they will produce a shield, which is perforated by two pores and between them by the spine itself. These two "primary aspinal pores" are characteristic of all Ceriaspida; among these _Dorataspis_ itself is the most simple form. Its shell exhibits therefore constantly forty aspinal pores, and besides these a variable number of "sutural pores" (in the sutures between the twenty plates). If in each suture there be only a single pore, we get on the whole fifty-two or fifty-four pores; if in each suture there be two or three pores, that number becomes doubled or tripled.

Subgenus 1. _Doratasparium_, Haeckel.

_Definition._--Shell with fifty-two sutures; four polar plates on each pole of the main axis meeting in one point (in the pole itself); therefore all eight polar plates pentagonal and of equal size. Spherical shell therefore composed of four (equatorial) hexagonal plates and of sixteen pentagonal (eight tropical and eight polar plates).

1. _Dorataspis fusigera_, n. sp. (Pl. 138, fig. 2).

Shell with fifty-two sutures and fifty-two sutural meshes, with four hexagonal and sixteen pentagonal plates. Both aspinal meshes of each plate elliptical, twice to four times as broad as the {814}sutural meshes. Radial spines in the outer half fusiform, somewhat longer than the inner cylindrical half.

_Dimensions._--Diameter of the shell 0.08 to 0.09, of the parmal meshes 0.1 to 0.2, of the sutural meshes 0.004 to 0.01.

_Habitat._--Central Pacific, Station 271, surface.

2. _Dorataspis macracantha_, n. sp.

Shell with fifty-two sutures and fifty-two sutural meshes; with four hexagonal and sixteen pentagonal plates. Both aspinal meshes of each plate circular, small, twice as broad as the small sutural meshes. Radial spines quadrangular, prismatic, their outer half twice to three times as long as the inner half.

_Dimensions._--Diameter of the shell 0.12, of the parmal pores 0.008, of the sutural meshes 0.004.

_Habitat._--South Pacific, Station 288, surface.

3. _Dorataspis macropora_, n. sp.

Shell with fifty-two sutures and one hundred to one hundred and fifty sutural meshes, with four hexagonal and sixteen pentagonal plates. Both aspinal meshes nearly circular, very large, five to ten times as broad as the small circular sutural meshes; the number of the latter is in this species multiplied, in each suture being two to three (commonly three) small pores. Radial spines in the outer half leaf-shaped, compressed, nearly lanceolate, longer than in the inner cylindrical half.

_Dimensions._--Diameter of the shell 0.16, of the parmal pores 0.03 to 0.04, of the sutural pores 0.004 to 0.006.

_Habitat._--Indian Ocean (Madagascar), Rabbe, surface.

Subgenus 2. _Dorataspidium_, Haeckel.

_Definition._--Shell with fifty-four sutures; four polar plates on each pole of the main axis different in pairs; two major hexagonal meeting in a polar suture (the "hydrotomical suture"); two minor pentagonal, not meeting together (separated by that hydrotomical suture). Spherical shell therefore composed of eight hexagonal plates (four equatorial and four polar) and by twelve pentagonal plates (eight tropical and four polar plates).

4. _Dorataspis loricata_, Haeckel.

_Dorataspis loricata_, Haeckel, 1862, Monogr. d. Radiol., p. 415, Taf. xxi. figs. 3-6.

Shell with fifty-four sutures and fifty-four sutural meshes, with eight hexagonal and twelve pentagonal plates. Both aspinal meshes of each plate kidney-shaped or roundish, nearly of the {815}same size as the sutural meshes. Radial spines cylindrical; their outer half on the pointed distal end two-edged and longer than the inner half.

_Dimensions._--Diameter of the shell 0.14, of its meshes 0.008 to 0.016.

_Habitat._--Mediterranean (Messina), North Atlantic (Canary Islands), Azores, surface.

5. _Dorataspis typica_, n. sp. (Pl. 138, figs. 4, 4_a_).

Shell with fifty-four crest-like sutures and fifty-four circular sutural meshes, with eight hexagonal and twelve pentagonal plates. Both aspinal meshes of each plate elliptical, twice to three times as broad as the sutural meshes. Aspinal meshes of the four equatorial plates twice as broad as those of the sixteen other plates. The meshes are surrounded by elevated and denticulated crests (incipient spine-sheaths). Radial spines compressed, more or less two-edged; outer pointed half somewhat larger than the inner half. (In this typical species the composition of the shell prevailing in the majority of Ceriaspida is very clear.)

_Dimensions._--Diameter of the shell 0.15 to 0.18, of the aspinal pores 0.02 to 0.03, of the sutural pores 0.01.

_Habitat._--Central Pacific, Stations 270 to 274, surface and in various depths.

6. _Dorataspis micropora_, n. sp. (Pl. 138, fig. 3).

Shell with fifty-four sutures and fifty-four very small sutural meshes, with eight hexagonal and twelve pentagonal plates. Both aspinal meshes of each plate elliptical, four to six times as broad as the sutural meshes. Radial spines in the outer half conical, somewhat shorter than in the inner cylindrical half.

_Dimensions._--Diameter of the shell 0.11, of the aspinal pores 0.01 to 0.02, of the sutural pores 0.003.

_Habitat._--North Pacific, Station 244, depth 2900 fathoms.

7. _Dorataspis gladiata_, n. sp.

Shell with fifty-four sutures and one hundred to one hundred and twenty sutural meshes, with eight hexagonal and twelve pentagonal plates. Both aspinal meshes elliptical, three times as broad as the small sutural meshes; commonly two meshes in each suture. Radial spines sword-shaped, two-edged, tapering from the shell towards the two ends. (Resembles _Belonaspis datura_, Pl. 139, fig. 9, but differs in the spherical shell, the equal size of the four equatorial spines, and the absence of by-spines.)

_Dimensions._--Diameter of the shell 0.12, of the aspinal pores 0.012, of the sutural pores 0.004.

_Habitat._--Indian Ocean (Madagascar), Rabbe, surface.

8. _Dorataspis polypora_, n. sp.

Shell with fifty-four sutures and one hundred and sixty to two hundred sutural meshes, with eight hexagonal and twelve pentagonal plates. Commonly three meshes (sometimes four) on {816}each suture. Both aspinal meshes kidney-shaped, four times as broad as the small sutural meshes. Radial spines thick, in the inner longer part cylindrical, in the outer shorter part conical. (Differs from all other species in the multiplication of the sutural pores.)

_Dimensions._--Diameter of the shell 0.2, of the aspinal pores 0.016, of the sutural pores 0.004.

_Habitat._--Equatorial Atlantic, Station 347, surface.

Genus 352. _Diporaspis_,[392] n. gen.

_Definition._--#Dorataspida# with twenty plates, which are perforated by forty aspinal pores (two pores in each plate). Surface of the shell without combs and dimples, but armed with numerous by-spines.

The genus _Diporaspis_ has the same characteristic structure of the shell as the typical _Dorataspis_, and differs from it only in the development of numerous by-spines on the surface. The number of the sutures between the twenty plates is sometimes fifty-two, at other times fifty-four, and in each suture we find occasionally a single pore, at other times two or three such pores.

Subgenus 1. _Diporasparium_.

_Definition._--Shell with fifty-two sutures, four polar plates on each pole of the main axis meeting in one common point; therefore all eight polar plates pentagonal and of equal size. Shell therefore composed of four (equatorial) hexagonal plates, and of sixteen pentagonal (eight tropical and eight polar) plates.

1. _Diporaspis nephropora_, n. sp. (Pl. 134, fig. 15).

Shell with fifty-two sutures and fifty-two sutural pores, with four hexagonal and sixteen pentagonal plates. Both aspinal pores of each plate kidney-shaped, about twice as broad as the circular sutural pores. Radial spines thin, cylindrical, longer than the radius. By-spines forked, only one-third as long as the radius.

_Dimensions._--Diameter of the shell 0.13, parmal pores 0.03, sutural pores 0.07.

_Habitat._--North Pacific, Station 244, surface.

2. _Diporaspis circopora_, n. sp.

Shell with fifty-two sutures and one hundred to one hundred and fifty sutural pores, with four hexagonal and sixteen pentagonal plates. Both aspinal pores of each plate circular, very large, six to eight times as broad as the small circular sutural pores (in each suture two to three pores). {817}Radial spines strongly compressed, two-edged; outer half shorter than the inner. By-spines undulate, half as long as the radius.

_Dimensions._--Diameter of the shell 0.12, of the parmal pores 0.02 to 0.03, of the sutural pores 0.003 to 0.004.

_Habitat._--South Pacific, Station 287, surface.

Subgenus 2. _Diporaspidium_, Haeckel.

_Definition._--Shell with fifty-four sutures, four polar plates on each pole of the main axis different in pairs: two major hexagonal meeting in a polar ("geotomical") suture, two minor pentagonal, not meeting together (separated by that suture). Shell therefore composed of eight hexagonal plates (four equatorial and four polar) and of twelve hexagonal plates (eight tropical and four polar).

3. _Diporaspis zygopora_, n. sp.

Shell with fifty-four sutures and fifty-four circular sutural pores: with eight hexagonal and twelve pentagonal plates. Both aspinal pores of each plate elliptical, three times as broad as the sutural pores. Radial spines compressed, two-edged; outer half shorter than the inner. By-spines very numerous, simple, one-third as long as the radius, forming coronels or elegant circles around the pores (a small coronel around each sutural pore, a large one around each couple of aspinal pores).

This typical species is nearly allied to _Dorataspis typica_ (Pl. 138, fig. 4), and may be derived from it by development of the coronels of by-spines.

_Dimensions._--Diameter of the shell 0.16, aspinal pores 0.03, sutural pores 0.01.

_Habitat._--Central Pacific, Station 271, surface

Genus 353. _Orophaspis_,[393] Haeckel, 1881, Prodromus, p. 468.

_Definition._--#Dorataspida# with twenty plates, which are perforated by forty aspinal pores (two pores in each plate). Surface of the shell without combs, dimples, and by-spines. Each radial spine bears outside of the shell two opposite free apophyses, which are either simple or branched.

The genus _Orophaspis_ differs not only from its ancestral form, _Dorataspis_, but from all other Dorataspida in the development of peculiar free apophyses on the radial spines, outside the shell. These apophyses, two being opposite on each spine, appear as a repetition of the primary apophyses of _Phractaspis_; they are either simple or branched, and sometimes the branches are united together, forming an outer free shield with two or four pores. These outer plates represent the beginning of a second outer shell and form the transition to _Phractopelta_, the ancestral form of the Phractopeltida.

{818}Subgenus 1. _Orophasparium_, Haeckel.

_Definition._--Free apophyses of the radial spines simple, not branched.

1. _Orophaspis astrolonche_, n. sp.

Parmal pores of the shell circular, twice as large as the sutural pores and as the breadth of the bars. Radial spines very long, three to six times as long as the diameter of the shell, compressed, two-edged; each with two simple, opposite, triangular apophyses; their distance from the shell equal to its diameter.

_Dimensions._--Diameter of the shell 0.05, parmal pores 0.004, sutural pores 0.002.

_Habitat._--North Pacific, Station 239, surface.

2. _Orophaspis gladiata_, n. sp.

Parmal pores of the shell circular, of the same size as the sutural pores and the bars. Radial spines thick, spindle-shaped, scarcely longer than the diameter of the shell, each with two simple opposite conical apophyses; their distance from the shell about equal to its radius.

_Dimensions._--Diameter of the shell 0.06, pores 0.003.

_Habitat._--Central Pacific, Station 265, surface.

Subgenus 2. _Orophaspidium_, Haeckel.

_Definition._--Free apophyses of the radial spines branched, their branches free (not anastomosing).

3. _Orophaspis furcata_, n. sp. (Pl. 133, fig. 6).

Parmal pores of the shell roundish or elliptical, three times as broad as the sutural pores and the bars. Radial spines very long, compressed, each with two opposite apophyses, which are simply forked; their distance from the shell somewhat greater than its diameter.

_Dimensions._--Diameter of the shell 0.06 to 0.08, parmal pores 0.006, sutural pores 0.002.

_Habitat._--Central Pacific, Station 274, surface.

4. _Orophaspis ramosa_, n. sp.

Parmal pores of the shell circular, of the same size as the sutural pores and the bars. Radial spines compressed, very long, each with two opposite apophyses, which are more or less irregularly branched (commonly between eight and twelve thin branches on each spine); their distance from the shell smaller than its diameter.

_Dimensions._--Diameter of the shell 0.08, pores 0.006.

_Habitat._--North-West Pacific, Station 235, surface.

{819}Subgenus 3. _Stegaspis_, Haeckel, 1881, Prodromus, p. 468.

_Definition._--Free apophyses of the radial spines branched, and by reunion of their anastomosing branches forming perforated shields.

5. _Orophaspis diporaspis_, n. sp.

Parmal pores of the shell circular, of the same size as the sutural pores and the bars. Radial spines sword-shaped, two-edged, very broad; each spine bears an elliptical free shield with two longish pores (opposite on the two flat sides of the sword). Distance of the twenty free two-pored shields from the shell about equal to its diameter.

_Dimensions._--Diameter of the shell 0.04, of the pores 0.004.

_Habitat._--South Pacific, Station 295, surface.

6. _Orophaspis tessaraspis_, n. sp.

Parmal pores of the shell roundish, somewhat larger than the sutural pores and the bars. Radial spines very long, compressed; each spine bears a roundish free shield with four irregular pores disposed in a cruciform manner, the two larger pores being opposite on the flat sides of the spine, the two smaller being opposite but on its two edges. Distance of the twenty free four-pored shields from the shell about equal to its radius.

_Dimensions._--Diameter of the shell 0.05, of the pores 0.003.

_Habitat._--North Pacific, Station 239, surface.

Genus 354. _Ceriaspis_,[394] Haeckel, 1881, Prodromus, p. 468.

_Definition._--#Dorataspida# with twenty plates, which are perforated by forty aspinal pores (two pores in each plate). Surface of the shell with numerous dimples, separated by a network of elevated combs. No by-spines.

The genus _Ceriaspis_ has the same structure of the shell, as its ancestral form _Dorataspis_, differing from it only in the development of high combs or crests, which form on the surface of the shell a peculiar elevated network. The dimples or funnel-shaped pits between these combs are either all or partly perforated by the pores of the shell. Both the aspinal pores of each plate are usually placed in one common dimple, whilst each sutural pore is placed in its peculiar smaller dimple.

Subgenus 1. _Ceriasparium_, Haeckel.

_Definition._--Shell-surface with seventy to one hundred or more small funnel-shaped dimples, each of which opens on the bottom by one pore or by a couple of {820}apertures; twenty larger dimples in the centre of the plates (each with a couple of aspinal pores) and fifty to one hundred or more smaller dimples, each of which contains one sutural pore. No blind dimples between the perforated dimples.

1. _Ceriaspis lacunosa_, n. sp.

Shell spherical with seventy-two funnel-shaped dimples, each of which is perforated on the bottom by one or two apertures; twenty larger dimples in the centre of the plates, each with two elliptical aspinal pores, and fifty-two smaller sutural dimples between them, each with one circular pore of half the size. No blind dimples. Radial spines quadrangular, stout; their outer part shorter than the inner.

_Dimensions._--Diameter of the shell 0.1, of the forty parmal pores 0.01, of the fifty-two sutural pores 0.005.

_Habitat._--South Atlantic, Station 330, surface.

2. _Ceriaspis scrobiculata_, n. sp.

Shell spherical, with seventy-four funnel-shaped dimples, each of which is perforated on the bottom by one or two apertures; twenty larger dimples in the centre of the plates, each with two kidney-shaped large pores, and fifty-four smaller dimples on the sutures, each with one circular pore of one-fourth of the size of the reniform pores. No blind dimples. Radial spines cylindrical, the outer part longer than the inner.

_Dimensions._--Diameter of the shell 0.12, of the forty parmal pores 0.016, of the fifty-four sutural pores 0.004.

_Habitat._--Central Pacific, Station 270, surface.

Subgenus 2. _Ceriaspidium_, Haeckel.

_Definition._--Shell-surface with funnel-shaped dimples (commonly one hundred and seventy-six or one hundred and eighty-two), which on the bottom are partly closed, partly perforated by one aperture (or by a pair of pores). The blind dimples are placed on the corners of the twenty plates, and are therefore either one hundred and four or one hundred and eight; if there be no polar suture, the blind dimples are one hundred and four (twenty-four on the four hexagonal equatorial plates, forty on the eight pentagonal tropical plates, and forty on the eight pentagonal polar plates); if, however, there be a polar suture on both main poles, the number of blind dimples is one hundred and eight (twenty-four on the four hexagonal equatorial and twenty-four on the four hexagonal polar plates, two opposite on each pole; forty on the eight pentagonal tropical plates and twenty on the four pentagonal polar plates, two opposite on each pole). Between the blind dimples there are usually seventy-two to seventy-four perforated {821}dimples, twenty larger parmal dimples (enclosing a radial spine and a couple of aspinal pores) and fifty-two to fifty-four sutural dimples (sometimes one hundred or more), each of which encloses one sutural pore.

3. _Ceriaspis inermis_, n. sp. (Pl. 138, fig. 5).

Shell spherical, with one hundred and seventy-six funnel-shaped dimples, one hundred and four of which are blind and seventy-two perforated; of the latter, each of the fifty-two smaller contains a single sutural pore, each of the twenty larger a couple of aspinal pores. The elliptical or kidney-shaped aspinal pores are about twice as broad as the circular sutural pores. Radial spines thin, compressed, two-edged; their outer prolongation very short, rudimentary, scarcely higher than the axis of the surrounding funnel, and projecting but slightly from its aperture.

_Dimensions._--Diameter of the shell 0.15, of the forty parmal pores 0.016, of the fifty-two sutural pores 0.008.

_Habitat._--South Pacific, Station 289, surface.

4. _Ceriaspis favosa_, n. sp. (Pl. 138, fig. 6).

Shell polyhedral (icosahedral), with one hundred and eighty-two funnel-shaped dimples, one hundred and eight of which are blind and seventy-four perforated; of the latter, each of the fifty-four smaller contains a single sutural pore, each of the twenty larger a couple of aspinal pores. All pores roundish, nearly of the same size. Radial spines thin, compressed, two-edged; their outer part somewhat longer than the inner.

_Dimensions._--Diameter of the shell 0.12 to 0.13, of the pores 0.01 to 0.015.

_Habitat._--Central Pacific, Station 274, surface.

5. _Ceriaspis icosahedra_, n. sp.

Shell polyhedral (icosahedral), with one hundred and eighty-two funnel-shaped dimples, one hundred and eight of which are blind and seventy-four perforated; of the latter, each of the fifty-four smaller contains one small sutural pore, each of the twenty larger a couple of aspinal pores. The kidney-shaped aspinal pores are very large, four to six times as broad as the small circular sutural pores. Radial spines strong, quadrangular, their outer part from two to three times as long as the inner part.

_Dimensions._--Diameter of the shell 0.16, of the parmal pores 0.015 to 0.02, of the sutural pores 0.003 to 0.004.

_Habitat._--Tropical Atlantic, Station 349, surface.

6. _Ceriaspis cicatricosa_, n. sp.

Shell spherical, with two hundred and fifty to three hundred (or more) small funnel-shaped dimples, the majority of which are blind, the minority perforated by pores; of the latter forty {822}are aspinal pores (two at the base of each spine), the others sutural pores. All pores nearly of the same size. As the shell of this species is very dark and thick-walled, it was impossible to obtain more information with regard to the pores. Radial spines very stout; the outer conical part shorter than the inner cylindrical part.

_Dimensions._--Diameter of the shell 0.2, of the pores 0.006 to 0.008.

_Habitat._--North Pacific, Station 236, surface.

Genus 355. _Hystrichaspis_,[395] n. gen.

_Definition._--#Dorataspida# with twenty plates, which are perforated by forty aspinal pores (two pores in each plate). Surface of the shell with numerous dimples, separated by a network of elevated combs. Numerous by-spines.

The genus _Hystrichaspis_ has the same structure with regard to the shell, as its ancestral form _Ceriaspis_, and differs from the latter only in possessing numerous by-spines. Moreover, in the former the dimples of the shell-surface are either all perforated by pores, or some of them are blind.

Subgenus 1. _Hystrichasparium_, Haeckel.

_Definition._--Shell with seventy to one hundred or more funnel-shaped dimples, each of which opens on the bottom by one aperture or by a couple of pores; twenty larger dimples in the centre of the plates (each with a couple of pores, sometimes also three couples) and fifty to one hundred or more smaller dimples, each of which contains one sutural pore. No blind dimples between the perforated dimples.

1. _Hystrichaspis pectinata_, n. sp. (Pl. 138, fig. 8).

Shell with numerous (one hundred to two hundred?) funnel-shaped dimples, each of which is pierced at the bottom by one or two pores; twenty larger dimples in the centre of the plates (each with two aspinal pores), and fifty to one hundred and fifty or more smaller dimples (each with one sutural pore). No blind dimples. Crests between the dimples armed with a continuous series of simple by-spines. Radial main spines stout, in the inner half cylindrical, in the outer conical, more or less compressed.

_Dimensions._--Diameter of the shell 0.13, of the pores 0.004 to 0.006.

_Habitat._--Tropical Atlantic, Station 352, surface.

2. _Hystrichaspis furcata_, n. sp. (Pl. 138, fig. 9).

Shell with numerous (one hundred to two hundred?) funnel-shaped dimples, each of which is pierced at the bottom by one or two pores; twenty larger dimples in the centre of the plates (each {823}with two large aspinal pores), and fifty to one hundred and fifty or more smaller dimples (each with one small sutural pore). No blind dimples. Crests between the dimples armed with forked by-spines. Radial main spines stout, leaf-shaped, tapering towards both ends.

_Dimensions._--Diameter of the shell 0.12, parmal pores 0.01, sutural pores 0.005.

_Habitat._--Central Pacific, Station 276, surface.

3. _Hystrichaspis cristata_, n. sp. (Pl. 138, fig. 11).

_Siphonasphis cristata_, Haeckel, 1882, Manuscript.

Shell with numerous (one hundred to two hundred?) funnel-shaped dimples, each of which is pierced at the bottom by one or more pores. Twenty larger dimples in the centre of the plates are pierced by the radial main-spines; among these fourteen contain each a couple of aspinal pores; six others are much larger, and contain each six larger pores; these six plates are two opposite equatorial plates and four polar plates, placed in the same meridian plane (the "hydrotomical plane"); in each of these six "hydrotomical dimples" two pores are placed opposite to one another on the two edges of the leaf-shaped spine, four others being opposite in pairs on both flat sides of it. By this peculiar structure this species connects the true _Hystrichaspis_ with _Hexalaspis_ and _Diploconus_; however the twenty spines are of equal length, and the shell continues to be spherical. The twenty radial main-spines are leaf-like and compressed. The crests between the dimples are dentated by a series of small by-spines.

_Dimensions._--Diameter of the shell 0.15, of the aspinal pores 0.01, of the sutural pores 0.005.

_Habitat._--North Pacific, Station 240, surface.

Subgenus 2. _Hystrichaspidium_, Haeckel.

_Definition._--Shell-surface with numerous funnel-shaped dimples (commonly one hundred and seventy-six to one hundred and eighty-two), which on the bottom are partly closed, partly perforated by one aperture (or by a pair of pores). The blind dimples are situated on the corners of the twenty plates; their number is commonly one hundred and four or one hundred and eight, sometimes more. The perforated dimples, alternating with the former, are usually seventy-two to seventy-four, sometimes more; twenty larger parmal dimples (each with a couple of aspinal pores, sometimes also with three such couples) and fifty-two to fifty-four sutural dimples, sometimes one hundred or more (each with one sutural pore). (Compare the definition of _Ceriaspidium_, p. 820.)

4. _Hystrichaspis dorsata_, n. sp. (Pl. 138, fig. 10).

Shell with one hundred and seventy-six funnel-shaped dimples, one hundred and four of which are blind and seventy-two perforated; of the latter, each of the fifty-two smaller contains a single {824}sutural pore, each of the twenty larger a couple of aspinal pores; the elliptical aspinal pores are twice as broad as the circular sutural pores. The crests between the dimples are armed with simple scattered short by-spines; usually in the nodal points, where three combs meet, there exist three or two divergent by-spines. The twenty radial main-spines are thin and long, compressed.

_Dimensions._--Diameter of the shell 0.22, of the aspinal pores 0.02, of the sutural pores 0.01.

_Habitat._--Central Pacific, Station 271, surface.

5. _Hystrichaspis armata_, n. sp.

Shell with one hundred and seventy-six funnel-shaped dimples, one hundred and four of which are blind and seventy-two perforated; of the latter, each of the fifty-two smaller contains a single sutural pore, each of the twenty larger a couple of aspinal pores. Crests between the dimples comb-like, armed with a series of simple by-spines. Twenty main-spines very stout, in the inner part cylindrical, in the outer shorter part conical.

_Dimensions._--Diameter of the shell 0.25, of the aspinal pores 0.02, of the sutural pores 0.01.

_Habitat._--South-East Pacific, Station 300, surface.

6. _Hystrichaspis sulcata_, n. sp.

Shell with one hundred and eighty-two funnel-shaped dimples, one hundred and eight of which are blind and seventy-four perforated; of the latter, each of the fifty-four smaller contains a single sutural pore, each of the twenty larger a couple of aspinal pores. All pores nearly of the same size, very small. Crests between the dimples very high, sulcated, on the free edge serrate with short very numerous, simple by-spines. Radial main-spines very stout and short, conical.

_Dimensions._--Diameter of the shell 0.2, of the pores 0.003.

_Habitat._--South Atlantic, Station 325, surface.

7. _Hystrichaspis foveolata_, n. sp.

Shell with very numerous (three hundred to four hundred?) small and deep funnel-shaped dimples, the majority of which are blind, the minority perforated; among the latter there are forty larger aspinal pores; the other smaller (scarcely half as large) pores are sutural. Crests between the dimples densely armed with simple short by-spines. Radial main-spines stout, leaf-shaped.

_Dimensions._--Diameter of the shell 0.12, of the aspinal pores 0.01, of the sutural pores 0.004.

_Habitat._--Tropical Atlantic, Station 338, surface.

8. _Hystrichaspis divaricata_, n. sp.

Shell with numerous (two hundred to three hundred?) funnel-shaped dimples, the majority of which are blind, the minority perforated; among the latter there are forty larger aspinal pores. {825}Crests between the dimples armed with long forked by-spines with divergent fork-branches. Radial spines cylindrical, very long and thick, longer than the diameter of the shell.

_Dimensions._--Diameter of the shell 0.14, aspinal pores 0.08, sutural pores 0.03.

_Habitat._--Central Pacific, Station 266, surface.

9. _Hystrichaspis fruticata_, n. sp. (Pl. 138, fig, 7).

Shell with numerous (one hundred and fifty to two hundred?) funnel-shaped dimples, the majority of which are blind, the minority perforated; forty aspinal pores elliptical, of the same size as the circular sutural pores. Crests between the dimples bearing elegant arborescent by-spines. Twenty radial main-spines long and thin, cylindrical or a little compressed.

_Dimensions._--Diameter of the shell 0.17, pores 0.01.

_Habitat._--Tropical Pacific, Station 275, surface.

10. _Hystrichaspis serrata_, n. sp.

Shell with numerous (two hundred to three hundred?) funnel-shaped dimples, the majority of which are blind, the minority perforated; forty aspinal pores of the same size as the sutural pores. Crests between the dimples covered with denticulated by-spines. Twenty radial main-spines compressed, two-edged, with serrated edges, about as long as the diameter of the shell.

_Dimensions._--Diameter of the shell 0.21, pores 0.012.

_Habitat._--North Pacific, Station 238, surface.

Genus 356. _Coscinaspis_,[396] n. gen.

_Definition._--#Doratispida# with twenty plates, which are perforated by eighty to two hundred or more parmal pores (two aspinal and two to ten or more coronal pores in each plate). Surface without by-spines.

The genus _Coscinaspis_, together with the following nearly allied genus _Acontaspis_, may be separated from the other Ceriaspida as a peculiar tribe, _Coscinaspida_. This tribe is characterised by the larger number of the parmal pores. Whilst in all other Ceriaspida this number is constantly forty (only two pores in each plate), here it may be from eighty to two hundred or more; in each shield the two primary "aspinal pores" are surrounded by a circle of two to ten or more (commonly eight to twelve) "coronal pores." The number of sutural pores in this group is also usually larger.

{826}Subgenus 1. _Coscinasparium_, Haeckel.

_Definition._--Plates of the shell smooth, without crests, not dimply.

1. _Coscinaspis peripora_, n. sp. (Pl. 138, fig. 1).

Shell thin walled, with smooth surface, without crests and dimples, perforated by pores of very different sizes. Forty aspinal pores, roundish or elliptical, of about the same size as the fifty or sixty violin-shaped sutural pores, and three to four times as broad as the small roundish coronal pores, which are irregularly formed and distributed, four to eight occurring on each plate (altogether one hundred to one hundred and twenty). Radial spines roundish, somewhat compressed; inner and outer half nearly of the same length.

_Dimensions._--Diameter of the shell 0.12, aspinal pores 0.01 to 0.012, coronal pores 0.003.

_Habitat._--North-West Pacific, Station 235, surface.

2. _Coscinaspis stigmopora_, n. sp.

Shell very thin walled, with smooth surface, without crests and dimples, perforated by pores of very different sizes. Forty aspinal pores, roundish, of about the same size as the fifty or sixty violin-shaped sutural pores, their diameter being about one-fifth of that of the plates. Coronal pores very numerous (two hundred to four hundred) and very small, irregularly scattered, ten to twenty occurring in each plate. Sutures strongly denticulated. Radial spines very thin and short, cylindrical.

_Dimensions._--Diameter of the shell 0.12 to 0.15, aspinal and sutural pores 0.01, coronal pores 0.001 to 0.003.

_Habitat._--North Pacific, Station 257, surface.

3. _Coscinaspis rhacopora_, n. sp.

Shell very thin walled, with smooth surface, without crests and dimples, perforated by very irregular pores of very different sizes and forms; commonly more or less lobed or sinuate. Forty aspinal pores and fifty to eighty sutural pores, larger than the numerous (one hundred to two hundred) irregularly scattered coronal pores. Sutures very sinuate. Radial spines cylindrical, thin and long.

_Dimensions._--Diameter of the shell 0.15 to 0.18, aspinal and sutural pores 0.01 to 0.02, coronal pores 0.001 to 0.005.

_Habitat._--Central Pacific, Station 274.

4. _Coscinaspis coscinopora_, n. sp.

Shell thin walled, with smooth surface, without crests and dimples, perforated by very numerous pores of circular form, but of different sizes. Forty aspinal pores and one hundred to two hundred {827}sutural pores much larger than the coronal pores, which are very small and very numerous (fifty to sixty on each plate). Sutures sinuate. Radial spines compressed, outer and inner half nearly of equal length.

_Dimensions._--Diameter of the shell 0.3, aspinal and sutural pores 0.01 to 0.015, coronal pores 0.001 to 0.002.

_Habitat._--Tropical Atlantic, Station 338, surface.

5. _Coscinaspsis polypora_, n. sp. (Pl. 136, fig. 8).

Shell very thin walled, with smooth surface, without crests and dimples, the two aspinal pores of each plate narrow, lanceolate, ten to twelve times as long as broad and half as long as the radius of each plate. Coronal pores irregular, polygonal, very numerous (two hundred to three hundred on each plate), commonly arranged more or less regularly in ten to twelve series parallel to the longitudinal diameter of the aspinal spines (ten to twenty pores in each series). Sutural pores irregular, polygonal, very numerous. Radial spines very thin and long, cylindrical.

_Dimensions._--Diameter of the shell 0.24; length of the aspinal pores 0.04, breadth 0.004; coronal and sutural pores 0.002 to 0.01.

_Habitat._--Tropical Atlantic, Station 349, surface.

6. _Coscinaspis orthopora_, n. sp.

Shell very thin walled, with smooth surface, without crest and dimples. All pores of nearly equal size and form; quadrangular, mostly rectangular; one hundred to two hundred, separated by two systems of parallel bars, perpendicular one to another, occur in each plate. Sutural pores mostly triangular. Radial spines very thin and long, cylindrical, somewhat compressed. (Similar to those of _Phatnaspis lacunaria_, Pl. 136, fig. 9, but spherical, not ellipsoidal.)

_Dimensions._--Diameter of the shell 0.2, pores 0.008 to 0.012.

_Habitat._--Central Pacific, Station 272, surface.

7. _Coscinaspis parmipora_, n. sp. (Pl. 137, fig. 9).

_Craniaspis parmipora_, Haeckel, 1866, Manuscript.

_Dorataspis parmipora_, Haeckel, 1881, Prodromus, Atlas.

Shell thin walled, with smooth surface, without crests and dimples. There are no sutural pores, since all twenty plates are connected by perfect sinuate sutures (therefore this excellent species may perhaps better represent a peculiar genus, called by me in 1866 _Craniaspis_). All pores are parmal pores; each plate with two elliptical aspinal pores, which are twice to five times broader than the numerous, roundish irregularly scattered coronal pores (thirty to fifty occurring on each plate). The radial spines are quite internal, that is, not prolonged on the outside of the shell; in this respect they resemble those of _Sphærocapsa_.

_Dimensions._--Diameter of the shell 0.16, aspinal pores 0.01, coronal pores 0.002 to 0.005.

_Habitat._--North Atlantic, Canary Islands (Lanzerote), surface.

{828}8. _Coscinaspis isopora_, n. sp. (Pl. 134, figs. 13, 14).

Shell thick walled, with smooth surface, without crests and dimples. All pores of the shell nearly of the same size and of similar form, about as broad as the bars between them, and about two hundred in number, viz., fifty to sixty (regularly fifty-two or fifty-four) sutural pores and one hundred and forty to one hundred and fifty parmal pores (forty aspinal kidney-shaped pores, and one hundred to one hundred and ten coronal circular pores: six in the angles of each equatorial plate, and five in the angles of each tropical and polar plate; if the disposition be quite regular, one hundred and four or one hundred and eight). Radial spines short, rudimentary, conical.

_Dimensions._--Diameter of the shell 0.2, of the pores and bars 0.012.

_Habitat._--Tropical Pacific, Station 218 (off New Guinea), surface.

Subgenus 2. _Coscinaspidium_, Haeckel.

_Definition._--Surface of the shell dimply, with a network of prominent crests.

9. _Coscinaspis ceriopora_, n. sp.

Shell thick-walled, with numerous (one hundred and sixty to two hundred?) funnel-shaped dimples, which are separated by prominent crests; on the bottom of each dimple there is a simple or double circular pore. If this species be quite regularly developed, it closely resembles the preceding, differing from it mainly in the prominent combs of the surface. It resembles also _Ceriaspis favosa_, Pl. 138, fig. 6; but whilst in this latter the majority of the dimples are blind, here they are all perforated. The twenty aspinal dimples (in the centre of each plate) present at the bottom a couple of pores, all other dimples a single pore. Among the latter there are fifty to sixty sutural pores and one hundred to one hundred and ten coronal pores, viz., six in each equatorial plate, and five in each of the other plates; but the number is not quite constant. Radial spines strong, in the inner part cylindrical, in the outer conical.

_Dimensions._--Diameter of the shell 0.15, of the pores and bars 0.01.

_Habitat._--Tropical Pacific, Station 215, surface.

Genus 357. _Acontaspis_,[397] Haeckel, 1881, Prodromus, p. 468.

_Definition._--#Dorataspida# with twenty plates, which are perforated by eighty to two hundred or more parmal pores (in each plate two aspinal and two to ten or more coronal pores). Surface covered with by-spines.

The genus _Acontaspis_ has the same characteristic structure of the shell as _Ceriaspis_, differing from it only in the presence of numerous by-spines. Each plate is perforated by four to sixteen or more (commonly ten to twelve) parmal pores, the two central of which are primary "aspinal pores," all the others being secondary "coronal pores."

{829}Subgenus 1. _Acontasparium_, Haeckel.

_Definition._--Plates of the shell not dimply, without prominent crests.

1. _Acontaspis lanceolata_, n. sp.

Shell thin walled, even, without crests and dimples between them, perforated by about three hundred pores of different sizes: forty aspinal pores elliptical, about as large as the irregular (fifty to sixty) sutural pores, and two to four times as broad as the small circular coronal pores (eight to twelve being on each plate, altogether about two hundred). Between the pores numerous short conical by-spines. Radial main spines lanceolate, about as long as the radius. (Similar to _Coscinaspis peripora_, Pl. 138, fig. 1, but with broad lanceolate spines and numerous short by-spines.)

_Dimensions._--Diameter of the shell 0.15, aspinal and sutural pores 0.012 to 0.015, coronal pores 0.004 to 0.008.

_Habitat._--South Atlantic, Station 325, surface.

Subgenus 2. _Acontaspidium_, Haeckel.

_Definition._--Surface of the shell dimply, with a network of prominent crests.

2. _Acontaspis hastata_, n. sp. (Pl. 134, fig. 16).

Shell thick walled, with numerous (one hundred and seventy to one hundred and ninety) dimples, which are separated by an elevated network of prominent crests. In the centre of each plate a larger dimple with a couple of aspinal pores, surrounded by a corona of ten or twelve smaller dimples, each of which contains a single pore (a coronal and sutural alternately). All pores circular or roundish, nearly of the same size. If the shell be quite regularly developed, there are fifty to sixty sutural pores and one hundred to one hundred and ten coronal pores (six in each equatorial plate, five in each of the other plates). The knobs of the meeting crests are conical, and bear each a simple short by-spine. Radial main spines compressed, at the distal end spear-shaped, with a rhomboidal plate below the apex, about as long as the radius.

_Dimensions._--Diameter of the shell 0.18, of the pores and bars 0.01.

_Habitat._--Western Tropical Pacific (off the Philippines), Station 215.

3. _Acontaspis furcata_, n. sp.

Shell thick walled, dimply, with a network of crests, of the same composition as in the foregoing species, with one hundred and seventy to one hundred and ninety dimples (twenty aspinal, one hundred to one hundred and ten coronal and fifty to sixty sutural dimples). All dimples and pores nearly of the same size. Each node of the crested network bears a stout by-spine, which is forked {830}on the base, with two divergent straight branches (similar to those of _Hystrichaspis furcata_, Pl. 138, fig. 9). Radial main spines two-edged, sword-like, nearly as long as the diameter of the shell.

_Dimensions._--Diameter of the shell 0.13, of the pores 0.008.

_Habitat._--Central Pacific, Station 272, surface.

4. _Acontaspis capillata_, n. sp.

Shell very dark and thick walled, non-transparent, with very numerous (three hundred to four hundred or more?) deep funnel-shaped dimples, each of which is perforated by a small circular pore (forty aspinal, two hundred to three hundred coronal, and fifty to one hundred sutural pores?). The high crests between the dimples bear very numerous simple by-spines, nearly half as long as the radius, so that the shell appears covered with hairs. Radial main spines very long and thin, cylindrical, longer than the diameter of the shell.

_Dimensions._--Diameter of the shell 0.2, of the pores 0.012.

_Habitat._--North Pacific, Station 244, surface.

Subfamily 2. TESSARASPIDA, Haeckel.

_Definition._--#Dorataspida# with twenty radial spines, each of which bears four crossed apophyses (opposite in pairs). The spherical shell is composed either of the meeting branches of these apophyses (Stauraspida), or of twenty perforated plates, produced by concrescence of their branches (Lychnaspida).

A. Tribe II. #Stauraspida#, Haeckel, 1881, Prodromus, p. 467.

_Definition._--#Dorataspida# with spherical shell, which is composed either of the meeting branches of the four crossed apophyses only, or exhibits four to twelve perforated plates which are produced by the crossed apophyses of four to twelve radial spines (but never of all twenty spines). Each plate bears four crossed pores.

Genus 358. _Stauraspis_,[398] Haeckel, 1881, Prodromus, p. 467.

_Definition._--#Dorataspida# without perforated plates; shell composed only of the meeting branches of the four crossed apophyses, which arise (opposite in pairs) from each radial spine. Condyles of the branch-ends without by-spines.

The genus _Stauraspis_ is the most simple and primitive form among all Tessaraspida, or that subfamily of Dorataspida, in which the shell is composed of twenty {831}radial spines, each of which bears four crossed apophyses. The subfamily may be divided into two different tribes, the Stauraspida and Lychnaspida. In the Stauraspida either all twenty spines, or a part of them, bear no perforated plates, and the shell is composed wholly or partially of the meeting branches of their apophyses. In the Lychnaspida, however, the four apophyses of each single spine form, by reunion of their recurved branches, a plate or shield with four crossed aspinal pores. The Lychnaspida represent therefore a more developed stage in the shell-formation than the simpler Stauraspida. _Stauraspis_, as the common ancestral form of both, may be derived phylogenetically from _Xiphacantha_ or _Stauracantha_, which differ only by the apophyses or branches of the apophyses not meeting. These branches (originally eight on each spine) are either simple or again branched.

Subgenus 1. _Staurasparium_, Haeckel.

_Definition._--Apophyses of the spines simple, not branched; therefore each spine with four sutural condyles.

1. _Stauraspis cruciata_, n. sp. (Pl. 134, fig. 5).

Radial spines thin, quadrangular, prismatic; outer and inner half nearly of equal length. Central bases pyramidal, with wing-like edges. Four apophyses of each spine simple, not branched, with thin condyles. Large meshes of the shell ten to twenty times as broad as the bars. This and the following species greatly resemble the simplest forms of _Phractaspis_ (Pl. 137, figs. 1, 2); they differ from these, however, by the equal size and distance of the four branches of each spine, which thus form a rectangular cross.

_Dimensions._--Diameter of the shell 0.1; breadth of the spines and bars 0.002.

_Habitat._--Central Pacific, Station 268, surface.

2. _Stauraspis xiphacantha_, n. sp.

Radial spines stout, cylindrical in the inner half, conical in the shorter outer half. Four apophyses of each spine simple, not branched, broad, with thick condyles. Meshes of the shell six to eight times as broad as the bars.

_Dimensions._--Diameter of the shell 0.12; breadth of the spines and bars 0.008 to 0.01.

_Habitat._--South Pacific, Station 290, surface.

Subgenus 2. _Stauraspidium_, Haeckel.

_Definition._--Apophyses of the spines branched; therefore each spine with eight to twenty or more sutural condyles.

{832}3. _Stauraspis furcata_, n. sp.

Radial spines thin, quadrangular, prismatic; outer and inner halves nearly of equal length. The four apophyses of each spine simply forked (or partly with bifid fork-branches); each spine with eight to twelve sutural condyles. Meshes of the shell ten to twenty times as broad as the bars.

_Dimensions._--Diameter of the shell 0.15; breadth of the spines and bars 0.003.

_Habitat._--Central Pacific, Station 266, surface.

4. _Stauraspis stauracantha_, n. sp. (Pl. 137, figs. 5, 6).

Radial spines thin, in the inner longer half cylindrical, in the outer half conical with thickened base. Four apophyses of each spine doubly forked or dichotomously (more or less irregularly) branched; each spine with sixteen to twenty-four sutural condyles. Meshes of the shell of very different sizes and forms; the largest ten to fifteen, the smallest two to three times as broad as the bars.

_Dimensions._--Diameter of the shell 0.14; breadth of of the spines 0.002 to 0.01, of the bars 0.002.

_Habitat._--Tropical Atlantic, Station 343, surface.

Genus 359. _Echinaspis_,[399] Haeckel, 1881, Prodromus, p. 467.

_Definition_--#Dorataspida# without perforated plates; shell composed only of the meeting branches of the four crossed apophyses, which arise (opposite in pairs) from each radial spine. Condyles of the branch-ends bearing by-spines.

The genus _Echinaspis_ exhibits the same structure of the shell as its ancestral form _Stauraspis_, and differs from it only in the development of by-spines on the sutural condyli.

1. _Echinaspis dichotoma_, n. sp.

Radial spines cylindrical, thin, outer half longer than the inner. Four apophyses of each spine simply forked (or partly with bifid fork-branches); therefore each spine usually possesses eight (sometimes ten to twelve) sutural condyles. Meshes of the shell ten to twelve times as broad as the bars. Each condyle bears a zigzag by-spine, half as long as the radius.

_Dimensions._--Diameter of the shell 0.12, of the spines 0.004 to 0.006.

_Habitat._--North Pacific, Station 253, surface.

{833}2. _Echinaspis diadema_, n. sp.

Radial spines thin and long, quadrangular, prismatic; outer half two to three times as long as the inner. Four apophyses of each spine simply forked (or partly with bifid fork-branches); each spine with eight to twelve sutural condyles. Meshes of the shell fifteen to twenty-five times as broad as the bars. Each condyle bears a simple bristle-shaped by-spine, nearly as long as the radius.

_Dimensions._--Diameter of the shell 0.11; breadth of the spines and bars 0.002.

_Habitat._--South Atlantic, Station 333, surface.

3. _Echinaspis echinoides_, n. sp. (Pl. 137, figs. 7,8).

Radial spines roundish, in the outer half conical, and two to three times as broad as in the inner half. Four apophyses of each spine doubly forked or dichotomously (more or less irregularly) branched; each spine with sixteen to twenty-four sutural condyles. Meshes of the shell four to eight times as broad as the bars. Each condyle bears a zigzag by-spine, one-third as long as the radius.

_Dimensions._--Diameter of the shell 0.15; breadth of the spines 0.004 to 0.01, of the bars 0.002.

_Habitat._--Central Pacific, Station 266, surface.

Genus 360. _Zonaspis_,[400] n. gen.

_Definition._--#Dorataspida# with four plates, each of which is perforated by four crossed aspinal pores; these four plates are formed by the united branches of the other spines (eight polar and eight tropical) form no lattice-plates by union. Each condyle bears a by-spine.

The genus _Zonaspis_ differs from all other Dorataspida in the peculiar formation of the four equatorial spines, which form by union of the recurved branches of their apophyses four perforated plates (each with four crossed pores), whilst the branches of the sixteen other plates do not unite to form plates, but simply meet the branches of the neighboring spines.

1. _Zonaspis fragilis_, n. sp.

Radial spines very thin and long, cylindrical. Four meshes of each equatorial plate pentagonal, ten to twelve times as broad as the bars. By-spines zig-zag, nearly as long as the radius.

_Dimensions._--Diameter of the shell 0.16, of the parmal pores 0.018.

_Habitat._--South Atlantic, Station 332, surface.

{834}2. _Zonaspis cingulata_, n. sp. (Pl. 134, figs. 3, 4).

Radial spines cylindrical in the inner half, with thickened pyramidal bases (fig. 3), conical in the outer half; both halves of equal length. The four meshes of each equatorial plate egg-shaped, four to six times as broad as the bars. By-spines zigzag, half as long as the radius.

_Dimensions._--Diameter of the shell 0.15, of the parmal meshes 0.015.

_Habitat._--Tropical Pacific (east coast off Philippines), Station 275, surface.

3. _Zonaspis æquatorialis_, n. sp. (Pl. 135, fig. 5).

Radial spines stout, cylindrical in the shorter inner half, conical in the longer outer half. The four meshes of each equatorial plate circular, only twice as broad as the bars. By-spines zigzag, nearly as long as the radius.

_Dimensions._--Diameter of the shell 0.11, of the parmal meshes 0.008.

_Habitat._--Equatorial Atlantic, Station 347, surface.

Genus 361. _Dodecaspis_,[401] n. gen.

_Definition._--#Dorataspida# with twelve plates, each of which is perforated by four crossed aspinal pores; these twelve plates are formed by the united branches of the apophyses of four equatorial and eight polar spines. The branches of the apophyses of the eight tropical spines form no lattice-plates by union. Each condyle bears a by-spine.

The genus _Dodecaspis_ differs from all other Dorataspida in the peculiar composition of its shell; twelve spines (four equatorial and eight polar spines) form by union of the branches of their apophyses twelve plates, each of which exhibits four crossed pores, whilst the eight other (tropical) spines form no perforated plates, but simply unite with the neighbouring spines by meeting branches. Some irregularity is often to be found in this genus; instead of four pores in each plate there may be two closed, the other two which are opposite being open. Several times I observed a peculiar "hemihedral" variety: only six spines of one meridian plane (the two equatorial and the four polar spines of the "hydrotomical" plane) exhibited complete shields, whilst the branches of the other fourteen plates remained open. This "hemihedral" form may perhaps represent a peculiar genus, _Hemiaspis_.

1. _Dodecaspis tricinata_, n. sp. (Pl. 134, fig. 1).

Radial spines thin and long, cylindrical. The four meshes of each equatorial and each polar plate of equal size, pentagonal, about eight times as broad as the bars. By-spines zigzag, nearly as long as the radius. In this species the hemihedral variety, _Hemiaspis_, often occurs.

_Dimensions._--Diameter of the shell 0.15, of the parmal pores 0.016.

_Habitat._--South-east Pacific (west coast of Patagonia), Station 302, surface.

{835}2. _Dodecaspis trizonia_, n. sp.

Radial spines thin, cylindrical in the longer inner half, conical in the shorter outer half. The four meshes of each equatorial and each polar plate of equal size, roundish or nearly circular, five to six times as broad as the bars. By-spines straight, denticulated, scarcely half as long as the radius.

_Dimensions._--Diameter of the shell 0.12, of the parmal pores 0.012.

_Habitat._--South-west Pacific (east coast of New Zealand), Station 169, surface.

B. Tribe II. #Lychnaspida#, Haeckel, 1881, Prodromus, p. 467.

_Definition._--#Dorataspida# with twenty perforated plates or fenestrated shields (each plate at least with four pores), produced by union of the branches of the four crossed apophyses, which arise, opposite in pairs, from each radial spine. The spherical shell is composed of the twenty plates united by sutures (rarely by concrescence).

Genus 362. _Tessaraspis_,[402] Haeckel, 1881, Prodromus, p. 468.

_Definition._--#Dorataspida# with twenty plates, which are perforated by eighty aspinal pores (four crossed pores in each plate). Surface smooth, without by-spines.

The genus _Tessaraspis_ introduces the series of Lychnaspida, which comprise all those Dorataspida in which the shell is composed of twenty plates, each of which is perforated by four primary aspinal pores. In _Tessaraspis_ and _Lychnaspis_ each plate exhibits only these four primary pores, whilst in _Icosaspis_ and _Hylaspis_ they become surrounded by a circle of secondary or coronal pores. If in _Stauraspis_, the common ancestral form of the Tessaraspida, the four crossed apophyses of each single radial spine became recurved and united together, we should have the typical plate of _Tessaraspis_, in which the piercing radial spine is surrounded by four crossed pores of equal size. The number of sutural pores, between the neighbouring plates, is variable; usually each plate is surrounded by a circle of eight to twelve sutural pores. The sutures between the meeting condyles of the apophyses usually remain open; but in some species they become obliterated (subgenus _Tessaraspidium_).

Subgenus 1. _Tessarasparium_, Haeckel.

_Definition._--Condyles of the neighbouring plates connected by permanent open sutures; therefore the whole shell is composed of twenty separated pieces of acanthin.

{836}1. _Tessaraspis arachnoides_, n. sp. (Pl. 136, fig. 1).

Parmal pores pentagonal, ten to twenty times as broad as the thin thread-like bars, on an average of about the same size as the irregular sutural meshes; the majority of the latter are either triangular or hexagonal. Radial spines very thin and long, cylindrical, their outer part two to four times as long as the inner. As the insertion of the spines is on the highest point of the plates, the shell becomes polyhedral (dodecahedral?).

_Dimensions._--Diameter of the shell 0.15 to 0.17, of the parmal meshes 0.02 to 0.025, sutural meshes 0.01 to 0.03, bars 0.002.

_Habitat._--Equatorial Atlantic, Station 347, surface.

2. _Tessaraspis pentagonalis_, n. sp.

Parmal meshes pentagonal, three to four times as broad as the thick bars, and on an average smaller than the irregular polygonal sutural meshes. Radial spines stout, quadrangular; their outer pyramidal part shorter than the inner prismatic part.

_Dimensions._--Diameter of the shell 0.12, of the parmal pores 0.01 to 0.012, bars 0.003.

_Habitat._--Central Pacific, Station 269, surface.

3. _Tessaraspis tetragonalis_, n. sp.

Parmal meshes tetragonal, or nearly square, six to eight times as broad as the thin bars, and on an average larger than the irregular polygonal sutural meshes. Radial spines thin, quadrangular, prismatic, their outer part longer than their inner.

_Dimensions._--Diameter of the shell 0.16, of the parmal pores 0.012 to 0.016, bars 0.002.

_Habitat._--South Pacific, Station 288, surface.

4. _Tessaraspis hexagonalis_, n. sp.

Parmal meshes hexagonal, ten to twelve times as broad as the thin bars, and on an average larger than the polygonal sutural meshes (the two proximal sides of each hexagonal parmal mesh two to three times as long as the four distal sides). Radial spines cylindrical, thin; their outer part longer than the inner.

_Dimensions._--Diameter of the shell 0.15, of the parmal pores 0.01 to 0.015, bars 0.001.

_Habitat._--North Pacific, Station 254, surface.

5. _Tessaraspis trigonalis_, n. sp.

Parmal meshes triangular, three to four times as broad as the thick bars, and on an average smaller than the irregular sutural meshes (in each plate all four parmal meshes of the same size, formed like an isosceles triangle, the distal base of which is somewhat curved, and convex towards {837}the periphery, whilst the two proximal sides are straight). Radial spines thick, rounded; their outer conical part shorter than the inner cylindrical part.

_Dimensions._--Diameter of the shell 0.1, of the parmal pores 0.01, of the sutural pores 0.01 to 0.02.

_Habitat._--Tropical Atlantic (near Ascension), Station 345, depth 2010 fathoms.

6. _Tessaraspis circularis_, n. sp.

Parmal meshes circular, all eighty of equal size, quite regular, five to six times as broad as the thick bars, on an average larger than the roundish irregular sutural meshes. Radial spines quadrangular, prismatic, the outer part longer than the inner.

_Dimensions._--Diameter of the shell 0.18, parmal pores 0.015 to 0.018, bars 0.003.

_Habitat._--South-east Pacific, Station 300, surface.

7. _Tessaraspis micropora_, n. sp.

Parmal meshes circular, very small, all eighty of the same size, regular, scarcely as broad as the separating thick bars, and much smaller than the large irregular sutural meshes. Radial spines rounded, their outer conical part about as long as the inner cylindrical part.

_Dimensions._--Diameter of the shell 0.08, of the parmal pores 0.003, of the sutural pores 0.005 to 0.015, bars 0.004.

_Habitat._--Western Tropical Pacific, Station 225, surface.

8. _Tessaraspis diodon_, Haeckel.

_Dorataspis diodon_, Haeckel, 1862, Monogr. d. Radiol., p. 417, Taf. xxii. figs. 1-5.

Parmal meshes roundish, for the most part nearly circular, three to four times as broad as the bars, and on an average smaller than the roundish sutural meshes. Radial spines in the inner part cylindrical; the outer part very short (only one-third or one-fourth of the radius), divided completely into two parallel conical pointed teeth by a deep incision.

_Dimensions._--Diameter of the shell 0.12, of the parmal pores 0.01 to 0.012, of the sutural pores 0.01 to 0.03, bars 0.004.

_Habitat._--Mediterranean (Messina), surface.

9. _Tessaraspis quadriforis_, n. sp.

Parmal meshes irregular, roundish, of nearly equal size, four to six times as broad as the bars, and on an average of the same size as the roundish sutural meshes. Radial spines quadrangular, prismatic in the inner part, which is somewhat longer than the conical outer part.

_Dimensions._--Diameter of the shell 0.16, of the pores 0.012 to 0.018, bars 0.003.

_Habitat._--North Atlantic, Canary and Cape Verde Islands, Station 353, surface.

{838}10. _Tessaraspis irregularis_, n. sp.

Parmal meshes irregular, roundish, of unequal size, three to six times as broad as the bars, and on an average larger than the irregular sutural meshes. Radial spines cylindrical, the outer part longer than the inner part.

_Dimensions._--Diameter of the shell 0.13, parmal pores 0.006 to 0.012, sutural pores 0.005 to 0.01; bars 0.002.

_Habitat._--Central Pacific, Station 270, surface.

Subgenus 2. _Tessaraspidium_, Haeckel.

_Definition._--Condyles of the neighbouring plates grown together and sutures obliterated; therefore the whole shell forms a single piece of acanthin.

11. _Tessaraspis quadrata_, n. sp.

_Tessaraspidium quadratum_, Haeckel, 1882, Manuscript.

Parmal meshes square, four times as broad as the thin bars, on an average of the same size as the polygonal sutural meshes. Radial spines stout, tetrapterous, prismatic, in the outer part longer than in the inner. Sutures of the shell completely obliterated, therefore the whole shell forms one piece.

_Dimensions._--Diameter of the shell 0.16, of the parmal pores 0.012, sutural pores 0.01 to 0.015.

_Habitat._--South Atlantic, Station 332, depth 2200 fathoms.

12. _Tessaraspis rotunda_, n. sp.

Parmal meshes circular, of equal size, twice as broad as the thick bars, on an average smaller than the roundish sutural meshes. Radial spines cylindrical in the inner part, which is somewhat longer than the outer conical part. Sutures of the shell completely obliterated, therefore the whole shell forms one piece.

_Dimensions._--Diameter of the shell 0.12, parmal pores 0.008, sutural pores 0.005 to 0.015.

_Habitat._--North Atlantic, Station 354, surface.

13. _Tessaraspis concreta_, n. sp. (Pl. 136 fig. 5).

Parmal meshes irregular, polygonal or roundish, six to eight times as broad as the narrow and high bars, much larger than the irregular sutural meshes. Radial spines leaf-shaped, compressed, two-edged, pointed at both ends; inner and outer part nearly of equal size. Shell very thick walled; meshes therefore funnel-shaped; sutures completely obliterated, therefore the whole shell forms a single piece.

_Dimensions._--Diameter of the shell 0.09, parmal pores 0.02, sutural pores 0.01.

_Habitat._--Central Pacific, Station 274, depth 2750 fathoms.

{839}Genus 363. _Lychnaspis_,[403] Haeckel, 1862, Prodromus, p. 468.

_Definition._--#Dorataspida# with twenty plates, which are perforated by eighty aspinal pores (four crossed pores in each plate). Surface covered with numerous by-spines.

The genus _Lychnaspis_, the largest and most common of all Dorataspida, exhibits the same structure of the shell as its ancestral form _Tessaraspis_, and differs from it only in the development of by-spines on the sutural condyles. Many species of this genus are very widely distributed, and appear in large numbers, and some of them are amongst the most graceful and elegant of the Radiolaria.

Subgenus 1. _Lychnasparium_, Haeckel.

_Definition._--Condyles of the neighbouring plates connected by permanent open sutures; therefore the whole shell is composed of twenty separate pieces of acanthin.

1. _Lychnaspis giltschii_, n. sp. (Pl. 135, fig. 3).

Parmal meshes pentagonal, about ten or twelve times as broad as the thin bars, on an average of the same size as the irregular polygonal sutural meshes. By-spines (two hundred to three hundred) very delicate, half as long as the radius, barbed, and zigzag. Radial main-spines very thin and long, straight, cylindrical; their outer part longer than the inner part.

_Dimensions._--Diameter of the shell 0.2, of the parmal pores 0.02, sutural pores 0.01 to 0.03, bars 0.002.

_Habitat._--Tropical Atlantic, Stations 338 to 348, surface.

2. _Lychnaspis capillaris_, n. sp.

Parmal meshes pentagonal, twenty to thirty times as broad as the very thin thread-like bars, on an average of the same size as the irregular polygonal sutural meshes. By-spines (two hundred to two hundred and fifty) very delicate, zigzag, with very small denticles, one-third as long as the radius. Radial main-spines very thin and long, cylindrical, more or less undulated.

_Dimensions._--Diameter of the shell 0.25, parmal pores 0.025, sutural pores 0.02 to 0.04, bars 0.001.

_Habitat._--North Pacific, Station 250, surface.

3. _Lychnaspis maxima_, n. sp.

Parmal meshes pentagonal, six to eight times as broad as the thick bars, for the most part larger than the irregular sutural meshes. By-spines (four hundred to five hundred) nearly as {840}long as the radius, zigzag, with short denticles. Radial spines very long and stout, quadrangularly-prismatic, with four smooth edges.

_Dimensions._--Diameter of the shell 0.3, parmal pores 0.03, sutural pores 0.01 to 0.025, bars 0.004.

_Habitat._--Central Pacific, Stations 271 to 274, surface.

4. _Lychnaspis serrata_, n. sp.

Parmal meshes pentagonal, three to four times as broad as the thick bars, smaller than the irregular sutural meshes. By-spines (two hundred to three hundred) scarcely one-third as long as the radius, zigzag, with strong denticles. Radial spines very long, stout, quadrangularly-prismatic, with four serrated edges.

_Dimensions._--Diameter of the shell 0.22, parmal pores 0.015, sutural pores 0.012 to 0.03, bars 0.004.

_Habitat._--South Atlantic, Station 330, surface.

5. _Lychnaspis wagenschieberi_, n. sp.

Parmal meshes tetragonal, nearly rhombic, three to four times as broad as the thick bars, smaller than the large irregular sutural meshes. By-spines (about two hundred) large, as long as the radius, with long recurved denticles, very zigzag. Radial main-spines very long, four-sided prismatic. This species differs by the form and size of the spines, and by the square form of the parmal pores from the similar _Lychnaspis polyancistra_, of which the late excellent engraver Wagenschieber, of Berlin, has given such a beautiful figure in my monograph (Taf. xxi. fig. 8).

_Dimensions._--Diameter of the shell 0.16, parmal pores 0.014, sutural pores 0.015 to 0.02, bars 0.004.

_Habitat._--Central Pacific, Station 266, surface.

6. _Lychnaspis polyancistra_, Haeckel.

_Dorataspis polyancistra_, Haeckel, 1862, Monogr. d. Radiol., p. 418, Taf. xxi. figs. 7-9.

Parmal meshes roundish, tetragonal, or nearly square, two to three times as broad as the thick bars, smaller than the irregular sutural meshes. By-spines (about two hundred) thin, half as long as the radius, zigzag, with blunt denticles. Radial main-spines stout, in the inner half cylindrical, in the outer half (of the same length) conical, pointed.

_Dimensions._--Diameter of the shell 0.12, parmal pores 0.012, sutural pores 0.01 to 0.04, bars 0.004.

_Habitat._--Mediterranean (Messina), surface.

{841}7. _Lychnaspis rottenburgii_, n. sp. (Pl. 135, fig. 4).

Parmal meshes roundish, about twice as broad as the thick bars, and for the most part smaller than the irregular sutural meshes. By-spines (about two hundred to two hundred and fifty) thin, zigzag, half as long as the radius. Radial main-spines very strong, cylindrical in the inner half, in the outer half much thicker and conical, pointed. I call this species in honour of my learned friend, the great patron of zoological studies, Mr. Paul Rottenburg, of Glasgow.

_Dimensions._--Diameter of the shell 0.15, parmal pores 0.012, sutural pores 0.01 to 0.03, bars 0.006.

_Habitat._--Central Pacific, Station 270, depth 2925 fathoms.

8. _Lychnaspis undulata_, n. sp. (Pl. 135, fig. 2).

Parmal meshes circular, twice as broad as the thick bars, on an average of the same size as the irregular sutural meshes. By-spines (one hundred and fifty to two hundred) very thin, barbed and zigzag, as long as the radius. Radial main-spines cylindrical; their outer pointed part longer than the inner part.

_Dimensions._--Diameter of the shell 0.1, parmal pores 0.01, sutural pores 0.01, bars 0.005.

_Habitat._--Tropical Atlantic, Station 343, surface.

9. _Lychnaspis longissima_, n. sp. (Pl. 134, fig. 6).

Parmal meshes circular, very small, of the same breadth as the thick bars, much smaller than the irregular sutural meshes. By-spines (one hundred to one hundred and ten) very long and thin, zigzag, twice as long as the diameter of the shell. Radial main-spines very long and strong, cylindrical (at the base quadrangular, pyramidal), four to six times as long as the diameter of the shell, and one fourth as thick as its radius.

_Dimensions._--Diameter of the shell 0.08, parmal pores 0.002, sutural pores 0.01 to 0.015, bars 0.003; length of the radial spines 0.3 to 0.5.

_Habitat._--Tropical Pacific (Philippines), Stations 200 to 215, surface.

10. _Lychnaspis minima_, n. sp. (Pl. 134, figs. 2, 7, 8).

Parmal meshes circular, very small, only half as broad as the thick bars, much smaller than the irregular sutural meshes. By-spines (one hundred to one hundred and ten) half as long as the radius, zigzag. Radial main-spines thick, in the inner part cylindrical, in the outer shorter part conical, of very variable size.

_Dimensions._--Diameter of the shell 0.05, parmal pores 0.002, sutural pores 0.006 to 0.012, bars 0.004.

_Habitat._--Antarctic Ocean, Station 154, surface.

{842}Subgenus 2. _Lychnaspidium_, Haeckel.

_Definition._--Condyles of the neighbouring plates grown together and sutures obliterated, therefore the whole shell forms a single piece of acanthin.

11. _Lychnaspis echinoides_, Haeckel.

_Haliomma echinoides_, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p.36, Taf. v. figs. 3, 4.

_Haliommatidium echinoides_, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 22.

_Haliommatidium echinoides_, Haeckel, 1862, Monogr. d. Radiol., p. 422.

Parmal meshes pentagonal or somewhat roundish, four times as broad as the bars, and of about the same size as the polygonal meshes. By-spines (about two hundred) short, zigzag. Radial spines thin; their outer conical part shorter than the inner cylindrical part. Sutures perfectly obliterated, but recognisable by the characteristic pair of divergent by-spines. (Some recent observations on this species, made during 1880 in Portofino, have convinced me that the interpretation of it given in my Monograph, 1862, _loc. cit._, was quite correct.)

_Haliomma ligurinum_, J. Müller (= _Haliommatidium ligurinum_, Haeckel, L. N. 16, p. 423) seems to be closely allied to the preceding.

_Dimensions._--Diameter of the shell 0.12 to 0.14, parmal pores 0.015, sutural pores 0.01 to 0.02, bars 0.004.

_Habitat._--Mediterranean, Nice, Saint Tropez (J. Müller); Portofino near Genoa (Haeckel).

12. _Lychnaspis haliommidium_, n. sp.

_Lychnaspidium haliommidium_, Haeckel, 1882, Manuscript.

Parmal meshes circular, twice as broad as the bars, smaller than the irregular sutural meshes. By-spines (about two hundred) barbed and zigzag, as long as the radius. Radial main-spines four-sided; their outer pyramidal part shorter than the inner prismatic part. Sutures perfectly obliterated.

_Dimensions._--Diameter of the shell 0.1, parmal pores 0.01, sutural meshes 0.015 to 0.02.

_Habitat._--South Atlantic, Station 335, depth 1425 fathoms.

13. _Lychnaspis rabbeana_, n. sp.

Parmal meshes circular, very small, of the same breadth as the bars, and much smaller than the irregular sutural meshes. By-spines (about one hundred) very long and thin, zigzag, about as long as the diameter of the shell. Radial main-spines cylindrical, thick, twice to three times as long as the diameter of the shell. Sutures perfectly obliterated, with thickened condyles. Named in honour of Captain Henrik Rabbe (of Bremen), to whom I am indebted for many new Indian and Atlantic Radiolaria.

_Dimensions._--Diameter of the shell 0.086, parmal pores 0.002, sutural pores 0.012, bars 0.002.

_Habitat._--Indian Ocean (Madagascar), Rabbe, surface.

{843}14. _Lychnaspis cataplasta_, n. sp.

Parmal pores very small, circular, half as broad as the bars, and much smaller than the irregular sutural pores. By-spines zigzag, as long as the diameter of the shell. Radial main-spines very thin and long, needle-shaped, cylindrical, five to six times as long as the diameter of the shell. Sutures perfectly obliterated. (This stunted species is one of the smallest of the Dorataspida.)

_Dimensions._--Diameter of the shell 0.05, parmal pores 0.0015, sutural pores 0.01, bars 0.002.

_Habitat._--Antarctic Ocean (off Kerguelen Island), Station 149, surface.

Genus 364. _Icosaspis_,[404] Haeckel, 1881, Prodromus, p. 468.

_Definition._--#Dorataspida# with twenty plates, which are perforated by one hundred and sixty to three hundred or more parmal pores (in each plate four crossed aspinal pores, and around them four to twelve or more coronal pores). Surface without by-spines.

The genus _Icosaspis_ and the closely allied _Hylaspis_ differ from all other Tessaraspida in the increased number of the parmal pores. Whilst this number in all other genera is eighty (only four crossed pores in each plate), here it amounts to one hundred and sixty to three hundred or more (sometimes more than a thousand); in each shield four primary, crossed "aspinal pores" being surrounded by a circle of four to twelve or more "coronal pores." The number of sutural pores in these two genera is also increased.

Subgenus 1. _Icosasparium_, Haeckel.

_Definition._--Condyles of the neighboring plates connected by permanent open sutures; therefore the whole shell composed of twenty separated pieces of acanthin.

1. _Icosaspis tabulata_, n. sp. (Pl. 136, fig. 2).

Parmal meshes all of nearly equal size and form, square, four times as broad as the bars, little larger than the triangular or polygonal sutural meshes. In each plate fifty to seventy (regularly sixty-four) quadrangular pores, viz., four primary square aspinal meshes, forming together a regular square surrounded by two to three coronas of rectangular (not quite regular) coronal meshes (six to eight in each transverse row). Radial spines tetrapterous, prismatic, with four thin and broad wings, from which arise the crossed bars between the four primary pores. Outer part of the spines longer than the inner. Commonly the condyles of the plates are only contiguous; sometimes they grow together, and this form approaches _Icosaspis tetragonopa_.

_Dimensions._--Diameter of the shell 0.25 to 0.3, of the pores 0.02, bars 0.005.

_Habitat._--North Pacific, Station 244, depth 2900 fathoms.

{844}2. _Icosaspis elegans_, n. sp. (Pl. 136, fig. 4; Pl. 134, fig. 9).

_Tessaraspis elegans_, Haeckel, 1882, Manuscript et Atlas.

Parmal meshes of very different size and form; in the centre of each plate a cross of four primary, pear-shaped "aspinal pores" (the largest of all); between them four secondary, little smaller, crossed, egg-shaped "angular pores"; around this rosette of eight larger meshes an inner complete circle of sixteen to twenty polygonal coronal pores, and an outer incomplete circle of thirty to forty very small marginal pores. The latter are smaller than the irregular sutural meshes, which are constricted in the middle, about forty to sixty around each plate. Radial spines thin, cylindrical, or a little compressed; their outer part longer than the inner. In this elegant and very common species the condyles usually remain separated by sutures; but sometimes the latter become obliterated, and the whole shell then forms a single piece, _Icosaspidium elegans_.

_Dimensions._--Diameter of the shell 0.2 to 0.3, commonly 0.25; larger parmal pores 0.02, smaller 0.001 to 0.003; sutural pores 0.005 to 0.015; bars 0.003.

_Habitat._--Tropical and Subtropical Atlantic, Canary Islands to Ascension Island, Stations 340 to 354, surface.

3. _Icosaspis cruciata_, n. sp. (Pl. 134, fig. 10).

Parmal meshes very different; in the centre of each plate a cross of four primary, nearly oblong, rectangular "aspinal pores"; between these four secondary, triangular, egg-shaped "angular pores" (the largest of all), and around this rosette a single circle of twelve to twenty-four small "coronal pores." The latter are of about the same size as the irregular sutural meshes, of which there are twenty to thirty around each plate. Radial spines thin, cylindrical, or a little compressed; their outer part longer than the inner.

_Dimensions._--Diameter of the shell 0.2 to 0.3, commonly 0.25; larger parmal pores 0.025, smaller 0.005 to 0.01; bars 0.005.

_Habitat._--Tropical and Subtropical Pacific, Sandwich to Marquesas Islands, Stations 256 to 274, surface.

4. _Icosaspis ornata_, n. sp.

Parmal meshes very different; in the centre of each plate a cross of four primary octagonal aspinal pores (the largest of all); between them four secondary, rhombic angular pores, and around this rosette a circle of twelve to sixteen smaller, polyhedral coronal pores, which are however larger than the irregular sutural pores (surrounding each plate to the number of twenty to thirty). Radial spines thin, quadrangular, prismatic; the outer part longer than the inner.

_Dimensions._--Diameter of the shell 0.25; larger parmal pores 0.03, smaller 0.01; sutural pores 0.004 to 0.008; bars 0.006.

_Habitat._--South Pacific, Station 295, depth 1500 fathoms.

{845}5. _Icosaspis spectabilis_, n. sp.

Parmal meshes very different; in the centre of each plate four very large, pentagonal aspinal pores, and around these two to three circles of smaller polygonal coronal pores, which are very numerous, and not larger than the small sutural pores. Radial spines quadrangular, prismatic, stout, very long; the outer part two to three times as long as the inner.

_Dimensions._--Diameter of the shell 0.4, of the larger aspinal meshes 0.03, of the outer meshes 0.002 to 0.02, bars 0.005.

_Habitat._--South Atlantic, Station 333, surface.

6. _Icosaspis multiforis_, n. sp.

Parmal meshes very numerous, more than one hundred in each plate; in the centre four larger pear-shaped pores, and around these four to five circles of smaller pores, gradually smaller towards the margin of the plate; the sutural meshes also very small and numerous (more than fifty around each plate), so that the number of all the pores together amounts to two thousand or even more. Radial spines thin, cylindrical, very long.

_Dimensions._--Diameter of the shell 0.32; larger aspinal pores 0.02, smaller 0.002 to 0.01; bars 0.003.

_Habitat._--Indian Ocean (Madagascar), Rabbe, surface.

Subgenus 2. _Icosaspidium_, Haeckel.

_Definition._--Condyles of the neighbouring plates grown together, and sutures obliterated; therefore the whole shell forms a single piece of acanthin.

7. _Icosaspis tetragonopa_, Haeckel.

_Haliommatidium tetragonopum_, Haeckel, 1862, Monogr. d. Radiol., p.421, Taf. xxii. fig. 13.

Parmal meshes all of nearly equal size and form, square, three times as broad as the bars, little larger than the sutural meshes. In each plate commonly sixteen equal square meshes, viz., four primary aspinal and twelve secondary, surrounding the former as a square corona. Radial spines tetrapterous, stout; the outer pyramidal half somewhat longer than the inner. This species differs from the similar _Icosaspis tabulata_ (Pl. 136, fig. 2) in the concrescence of the sutures, the smaller number of pores, and the form of the stouter spines. The figure in my Monograph, drawn from a broken fragment, is not quite correct.

_Dimensions._--Diameter of the shell 0.18, pores 0.009, bars 0.003.

_Habitat._--Mediterranean (Messina, Corfu), surface.

8. _Icosaspis icosahedra_, n. sp.

Parmal meshes of different size and form; in the centre of each plate a cross of four pentagonal, primary aspinal pores, surrounded by a complete corona of twelve to sixteen polygonal coronal {846}pores and an incomplete corona of thirty to forty very small marginal pores; the latter are not to be distinguished from the pores of the obliterated sutures. Radial spines quadrangular, the outer pyramidal part shorter than the inner prismatic part. Condyles grown together. As the plates are quite even, the shell becomes icosahedral.

_Dimensions._--Diameter of the shell 0.16, pores 0.002 to 0.02, bars 0.005.

_Habitat._--North Pacific, Station 241, surface.

9. _Icosaspis icosastaura_, n. sp. (Pl. 136, fig. 3).

_Tessaraspis icosastaura_, Haeckel, 1882, Manuscript et Atlas.

Parmal plates of different size and form; in the centre of each plate a cross of four larger primary, pyriform aspinal pores; between these four smaller roundish angular pores, and around this rosette a circle of ten to twenty (commonly sixteen) coronal pores, little larger than the very small sutural pores. Radial spines very thin and long, cylindrical or bristle-shaped. Condyles grown together; no suture visible.

_Dimensions._--Diameter of the shell 0.14; larger pores of the cross 0.01, smaller pores 0.002 to 0.008; bars 0.002 to 0.004.

_Habitat._--Central Pacific, Station 268, surface.

Genus 365. _Hylaspis_,[405] n. gen.

_Definition._--#Dorataspida# with twenty plates, which are perforated by one hundred and sixty to three hundred or more parmal pores (in each plate four crossed aspinal pores, and around them four to twelve or more coronal pores). Surface covered with numerous by-spines.

The genus _Hylaspis_ exhibits the same structure of the shell as the nearly allied ancestral genus _Icosaspis_, and differs from it only in the development of by-spines. Some species of these two genera exhibit the highest degree of complication in the structure of the shell seen among the Dorataspida.

1. _Hylaspis serrulata_, n. sp. (Pl. 135, fig. 1).

Parmal meshes four hundred to five hundred; in the centre of each plate a cross of four very large pentagonal or roundish aspinal pores, and around this a circle of sixteen to twenty much smaller irregular, polygonal, coronal pores; the latter of about the same size as the sutural pores. On each condyle one thin zigzag-shaped by-spine, nearly as long as the radius. Twenty radial spines very long, quadrangular, prismatic; on the inside thinner and smooth, on the outside thickened, and armed with four rows of recurved teeth, serrated.

_Dimensions._--Diameter of the shell 0.18, aspinal spines 0.02, other pores 0.002 to 0.01, bars 0.003.

_Habitat._--South Atlantic, Station 326, surface.

{847}2. _Hylaspis coronata_, n. sp.

Parmal meshes five hundred to six hundred; in the centre of each plate a cross of four long rectangular aspinal pores, between these four larger egg-shaped angular pores; around this rosette a circle of sixteen to twenty much smaller, irregular, roundish, coronal pores; the latter about of the same size as the sutural pores. On each condyle one bearded by-spine about one-third or one-fourth as long as the radius. Twenty radial spines, very long, smooth, quadrangular, prismatic.

_Dimensions._--Diameter of the shell 0.25, aspinal pores 0.02, other pores 0.005 to 0.01, bars 0.004.

_Habitat._--Central Pacific, Station 271, surface.

3. _Hylaspis barbata_, n. sp.

Parmal meshes twelve hundred to sixteen hundred; in the centre of each plate a cross of four large, somewhat oblong, octahedral aspinal pores, between these four rhombic smaller angular pores; around this rosette an inner circle of twelve to sixteen larger and an outer circle of fifty to sixty very small coronal pores; the latter smaller than the sutural pores. On each condyle one bristle-shaped zigzag by-spine, with recurved thin hooks, half as long as the radius. Twenty radial spines, very long, cylindrical, smooth.

_Dimensions._--Diameter of the shell 0.25 to 0.3, aspinal pores 0.022, other pores 0.002 to 0.015, bars 0.002.

_Habitat._--South Pacific, Station 295, surface.

Family XLI. #PHRACTOPELTIDA#, Haeckel (Pl. 133, figs. 1-6).

_Phractopeltida_, Haeckel, 1881, Prodromus, p. 468.

_Definition._--ACANTHARIA with double spherical lattice-shell, composed of the branched apophyses of twenty radial spines meeting in its centre, and disposed according to the Müllerian law of Icosacantha. Central capsule spherical, enclosing the inner and surrounded by the outer concentric shell.

The family #Phractopeltida# differs from all other ACANTHARIA in the development of a double spherical shell, composed of two concentric lattice-spheres, which are united by twenty radial spines meeting in the common centre. We could therefore oppose the Phractopeltida as _Diplophracta_ to all other #Acanthophracta# as _Haplophracta_ (with simple shell). The former exhibit a relation to the latter, similar to that exhibited by the Dyosphærida to the simple Monosphærida among the #Sphæroidea#.

In my Monograph (1862, p. 423) I described only one genus appertaining to this family, _Aspidomma_. I founded it upon the singular _Phractopelta_, described by {848}J. Müller as _Haliomma hystrix_. A second species of _Aspidomma_, the _Acanthometra mucronata_ of J. Müller, was probably an _Astrolonche_. At that time I placed _Aspidomma_ among the Haliommatida, led by the erroneous opinion that it might represent a transition-form between _Dorataspis_ and _Haliomma_. But I afterwards gave up this view, as I was convinced that there is no true phylogenetic connection between the acanthinic Dorataspida (_Actipylea_) and the siliceous Haliommatida (_Peripylea_). Therefore in my Prodromus (1881, p. 468) I placed _Aspidomma_ among the Dorataspida and changed its name to _Phractopelta_, to avoid further confusion with the unrelated Ommatida (#Sphæroidea#). It formed there, with three nearly related genera, the "subfamily Phractopeltida," which we now advance to the higher rank of a separate family. (By a typographical mistake the words are printed in the Prodromus _Phractopelma_ and Phractopelmida, &c., instead of _Phractopelta_ and Phractopeltida, &c.). The detection of other new species appertaining to this family, and a closer anatomical investigation of them, has now led to the distinction of five different genera, characterised by other differences than were employed in 1881 in the provisional system of the "Prodromus."

The two concentric spherical lattice-shells of the Phractopeltida, connected by radial beams, correspond perfectly to those of the double-shelled Dyosphærida (_Haliomma_, _Diplosphæra_, &c.), and in both cases we may call the smaller inner the "medullary shell," and the larger outer the "cortical shell." There is no doubt that the double-shelled Phractopeltida must be derived phylogenetically from the simple-shelled Dorataspida (just as we derive the double Dyosphærida from the simple Monosphærida). But it is not yet possible to decide positively which of the two shells is the first formed. Probably the small inner or medullary shell of the Phractopeltida is the first formed, and corresponds to the simple spherical lattice-shell of the Dorataspida; and the larger outer or cortical shell of the former is a later new formation, absent in the latter family. This opinion seems to be confirmed by the genus _Orophaspis_, the only form among the Dorataspida, in which the radial spines outside the shell bear free latticed apophyses. If these twenty apophyses grow further and meet one another, the second or outer shell of _Phractopelta_ may be formed. But some objections may be raised to this opinion from the peculiar structure and the very small size of the inner shell; and there is some possibility that this latter is a secondary later product inside of the primary cortical shell. The probably phylogenetic series which reveals the origin of the Phractopeltida is the following:--_Acanthometron_, _Zygacantha_, _Lithophyllium_, _Phractacantha_, _Doracantha_, _Dorataspis_, _Orophaspis_, _Phractopelta_.

The twenty radial spines exhibit in all Phractopeltida the same characteristic position and relation as in all other Icosacantha, and are constantly arranged according to the Müllerian law in four meridian planes, their distal ends falling into five parallel zones. Their distinction in the majority of the Phractopeltida is not difficult, {849}since the spines of the different zones bear apophyses of different shapes. Sometimes the four equatorial spines are stouter than the sixteen other spines, and often the eight tropical spines are somewhat different in form from the eight polar and from the four equatorial spines. The length of all twenty spines is commonly equal. Their form is usually more or less compressed, two-edged (as in _Zygacantha_), more rarely cylindrical (as in _Acanthometron_), or somewhat quadrangular (but not truly prismatic); therefore the transverse section of the spines is commonly elliptical or lanceolate, rarely circular or rhombic, never square; this seems to indicate their origin from _Zygacantha_. As in all ACANTHARIA, the spines consist of acanthin, not of silex. Their central ends are either perfectly grown together, and form a single star of acanthin, or the triangular faces of their small pyramidal bases are supported one upon another, without true concrescence.

The apophyses of the radial spines, by which the two concentric spherical shells are formed, seem to be constantly four on each spine, two being opposite in each shell. The proximal pair of opposite apophyses, forming the inner or medullary shell, is constantly much smaller than the distal pair composing the outer or cortical shell (Pl. 133, fig. 5). The proximal pair corresponds probably to the two primary apophyses of the Diporaspida (_Phractaspis_, _Dorataspis_, &c.), whilst the distal pair corresponds to the free apophyses of _Orophaspis_ (Pl. 133, fig. 6). Therefore the Phractopeltida may be derived phylogenetically from the Diporaspida (not from the Tessaraspida). In the common ancestral genus of this family, _Phractopelta_, the free part of the radial spines (outside the outer shell) is quite simple, without free apophyses; in all other genera of the family that free part of the spines (either in all twenty spines or only in some of them) bears a third pair of lateral apophyses; these may be either simple or branched or even latticed; but the outer apophyses (of the third rank) remain constantly free, and a third lattice-shell is never formed by union of their edges (Pl. 133, figs. 2-4).

The inner lattice-shell of the Phractopeltida, or their "medullary shell," is constantly very small (commonly 0.03 to 0.05 mm. in diameter, rarely more). Its structure is difficult to make out; in the unbroken shell it is concealed by the dense network of the outer shell; in the broken shell it is commonly destroyed. Usually the pores of the inner shell are very small, circular or subcircular, scarcely as broad as the small separating bars. In the majority of Phractopeltida their number seems to be about forty, being probably the forty primary aspinal pores of the Diporaspida; in some species this number seems to be exceeded, so that perhaps some sutural pores may exist between the aspinal pores; but commonly the twenty plates composing the inner shell (each with two aspinal pores) seems to grow together perfectly by their meeting edges, so that there are no sutural pores between them. Evident sutures were not recognisable in the inner shell of any Phractopeltida.

{850}The outer lattice-shell of the Phractopeltida, or their "cortical shell," is at least twice as broad, commonly about three times as broad, as the enclosed inner shell; it is much more varied in composition than the latter. Like the greater part of the Dorataspida we may distinguish here in the lattice-work two kinds of pores--parmal pores and sutural pores. The parmal pores are produced by the union of the meeting branches of the apophyses of each single spine, and are therefore visible on each isolated spine; whilst the sutural pores are formed by the meeting branches of the apophyses of neighbouring spines. The distinction of the parmal and the sutural pores, easy in most Dorataspida, is difficult in most Phractopeltida, because the sutures between the meeting branches are usually very early obliterated. However, the place of the obliterated suture is often indicated by the thickened condyles of the apophyses on both sides of the suture. Commonly also the form of the sutural pores is much more irregular than that of the parmal pores; the former are more or less constricted in the middle by the intumescence of the sutural condyles, whilst the latter are more roundish, elliptical, kidney-shaped, or square. The number of the pores in the outer shell in the typical normal form of Phractopeltida seems to be the same as in the most species of _Dorataspis_, _Diporaspis_, &c., between ninety and one hundred, viz., forty parmal pores and from fifty to sixty sutural pores. However, in many species this number is increased. Since in all Phractopeltida, each of the twenty plates is composed only of the meeting branches of two opposite apophyses, we find originally in each plate only two primary parmal pores or "aspinal pores." But in some species there occur four, six, or more pores in each plate; in this case two of them only are aspinal pores, all the others being "coronal pores." Moreover, in those species which exhibit on the base of each spine in the outer shell four crossed pores (Pl. 133, fig. 2), there are not four equivalent aspinal pores (as in the Tessaraspida), but the two opposite are primary or aspinal pores and the other two (different from them in size and form) coronal pores. However, the number of coronal pores in the Phractopeltida is never so large as in many Dorataspida, and the same holds good also for the increasing number of the irregular sutural pores. In none of the species observed does the total number of the pores in the outer shell reach two hundred.

The original mode of development of the apophyses composing the outer shell seems to be imitated by the free apophyses of the third order, which are developed from the radial spines outside the outer shell in all Phractopeltida, with the single exception of the simple ancestral genus _Phractopelta_. These apophyses of the third rank are also originally constantly two, opposite to one another (after the type of _Lithophyllium_, _Dorataspis_, &c.). Commonly they do not remain simple, but become branched, and by communication of the neighbouring branches small lattice-plates arise. Originally each of these free lattice-plates has only two parmal pores, but the number of the parmal pores increases afterwards, so that we may distinguish two (primary) {851}aspinal pores, and two, four, or more (secondary) coronal pores. In the majority of species the two opposite apophyses are first crossed at right angles by a transverse beam, and the two parallel transverse beams are again crossed by perpendicular tertiary branches (again parallel to the apophyses). In this case the network of the free lattice-plates becomes more or less rectangular. But in other species the ramification of the apophyses assumes more the form of bifurcation or of irregular branching. As already said, the neighbouring free lattice-plates of this third order never meet, and therefore a complete third shell is never formed.

The different genera of Phractopeltida exhibit very remarkable differences in the development of free apophyses (or lattice-plates of the third order). Whilst in the numerous species of the ancestral genus _Phractopelta_ all twenty spines remain simple, without such apophyses, only in a single observed species (representing the genus _Pantopelta_) were all twenty spines protected by them. In the three other genera only one part of the spines bears free apophyses, but not the other part. The most frequent form is _Dorypelta_ (Pl. 133, fig. 2); here eight spines are simple (four equatorial and four polar spines of the hydrotomical plane), whilst twelve spines bear apophyses (eight tropical and four polar spines of the geotomical plane). In _Octopelta_ the eight tropical spines only bear apophyses, whilst the twelve other (four equatorial and eight polar) are simple. In _Stauropelta_ finally the four equatorial spines only are simple, whilst the sixteen other bear free apophyses (eight tropical and eight polar spines).

_The Central Capsule_ of the Phractopeltida is constantly spherical, and enclosed between the two concentric spherical shells; it is therefore larger than the inner and smaller than the outer shell. Its wall is pierced by the twenty radial beams connecting the two shells. The shape of the central capsule and of the enveloping calymma is the same as in the other #Acanthophracta# and specially in the Dorataspida.

_Synopsis of the Genera of Phractopeltida._

{All twenty spines without { apophyses in the free All twenty spines of the { external part, 366. _Phractopelta_. same form, { {All twenty spines with { apophyses in the free { part, 367. _Pantopelta_.

{Eight tropical spines with { apophyses, twelve others { (eight polar and four { equatorial) simple, 368. _Octopelta_. { {Twelve radial spines Twenty radial spines, { (eight tropical and four partly without, partly { polar) with apophyses, with apophyses in the { eight others (four polar free external part, { and four equatorial) { simple, 369. _Dorypelta_. { {Sixteen radial spines { (eight tropical and { eight polar) with { apophyses, four { equatorial, simple, 370. _Stauropelta_.

{852}Genus 366. _Phractopelta_,[406] Haeckel, 1881, Prodromus, p. 468.

_Definition._--#Phractopeltida# with twenty simple radial spines, bearing no free apophyses outside the outer shell.

The genus _Phractopelta_ is the most simple form among the Phractopeltida, and may be regarded as the common ancestral form of this family. All twenty spines are of nearly equal form and size, and bear no free apophyses on their free part, outside the two concentric shells. _Phractopelta_ may be derived from _Orophaspis_ by further development of the free apophyses, which by union of their branches form a second outer shell around the primary shell of that Dorataspid.

Subgenus 1. _Phractopeltaris_, Haeckel.

_Definition._--Outer shell composed of twenty separated plates, the sutures of their meeting condyles not being grown together.

1. _Phractopelta dorataspis_, n. sp. (Pl. 133, fig. 1).

Outer shell composed of twenty plates, the meeting condyles of which are separated by permanent sutures. Each plate commonly with two elliptical aspinal pores, which are two to three times as broad as the irregular sutural pores. Radial spines (in the outer free part) compressed, linear, twice as long as the diameter of the shell.

_Dimensions._--Diameter of the outer shell 0.11, of the inner 0.05.

_Habitat._--North Pacific (off Japan), Station 239, surface.

2. _Phractopelta dyadopora_, n. sp.

Outer shell composed of twenty plates, the meeting condyles of which are separated by permanent sutures. Each plate commonly with two kidney-shaped aspinal pores, which are three to four times as broad as the irregular sutural pores. Radial spines conical, about as long as the radius of the shell.

_Dimensions._--Diameter of the outer shell 0.08, of the inner 0.04.

_Habitat._--North Pacific, Station 256, surface.

3. _Phractopelta diporaspis_, n. sp.

Outer shell composed of twenty plates, the meeting condyles of which are separated by permanent sutures. Each plate commonly with two quadrangular aspinal pores, which are four to five times {853}as broad as the irregular sutural pores. Radial spines compressed, sword-shaped, about as long as the diameter of the shell.

_Dimensions._--Diameter of the outer shell 0.09, of the inner 0.04.

_Habitat._--South Atlantic, Station 332, surface.

4. _Phractopelta tessaraspis_, n. sp.

Outer shell composed of twenty plates, the meeting condyles of which are separated by permanent sutures. Each plate commonly with four crossed, quadrangular, aspinal pores, the two opposite of which are much larger than the two others. Sutural pores small, roundish. Radial spines compressed, linear, about twice as long as the diameter of the shell.

_Dimensions._--Diameter of the outer shell 0.084, of the inner 0.032.

_Habitat._--North Pacific (off Japan), Station 238, surface.

5. _Phractopelta tetradopora_, n. sp.

Outer shell composed of twenty plates, the meeting condyles of which are separated by permanent sutures. Each plate commonly with four crossed quadrangular (or nearly circular) aspinal pores, all of nearly the same size. Sutural pores polygonal or roundish. Radial spines cylindrical, two to three times as long as the diameter of the shell.

_Dimensions._--Diameter of the outer shell 0.11, of the inner 0.045.

_Habitat._--North Pacific, Station 253, surface.

6. _Phractopelta hexadopora_, n. sp.

Outer shell composed of twenty plates, the meeting condyles of which are separated by permanent sutures. Each plate commonly with six aspinal pores, the two opposite of which are much larger than the four others. Sutural pores small, roundish. Radial spines compressed, two-edged, larger than the diameter of the shell.

_Dimensions._--Diameter of the outer shell 0.1, of the inner 0.04.

_Habitat._--Central Pacific, Station 272, surface.

7. _Phractopelta octadopora_, n. sp.

Outer shell composed of twenty plates, the meeting condyles of which are separated by permanent sutures. Each plate commonly with eight aspinal pores, the four crossed being larger than the four others alternating with them. Sutural pores irregular. Radial spines conical, shorter than the diameter of the shell.

_Dimensions._--Diameter of the outer shell 0.12, of the inner 0.04.

_Habitat._--Indian Ocean (Cocos Islands, surface), Rabbe.

{854}Subgenus 2. _Phractopeltidium_, Haeckel.

_Definition._--Outer shell composed of twenty united plates, the sutures of their meeting condyles being grown together.

8. _Phractopelta aspidomma_, n. sp.

Outer shell composed of twenty united plates, the meeting condyles of which are grown together. On the base of each radial spine (where its outer free part arises from the surface of the outer shell), two large elliptical aspinal pores, two to four times as large as the other roundish pores. Radial spines compressed, sword-shaped, about as long as the radius of the shell.

_Dimensions._--Diameter of the outer shell 0.1, of the inner 0.05.

_Habitat._--Equatorial Atlantic, Station 347, surface.

9. _Phractopelta haliomma_, n. sp.

Outer shell composed of twenty united plates, the meeting condyles of which are grown together. On the base of each radial spine two large kidney-shaped aspinal pores, little larger than the other irregular pores. Radial spines compressed, linear, two-edged, much longer than the diameter of the shell.

_Dimensions._--Diameter of the outer shell 0.09, of the inner 0.03.

_Habitat._--South Pacific, Station 295, surface.

10. _Phractopelta tessaromma_, Haeckel.

Outer shell composed of twenty united plates, the meeting condyles of which are grown together. On the base of each radial spine four crossed egg-shaped aspinal pores, two opposite of which are much larger than the two others. Sutural pores irregular. Radial spines cylindrical or little compressed, thin, longer than the diameter of the shell.

_Dimensions._--Diameter of the outer shell 0.1, of the inner 0.04.

_Habitat._--Central Pacific, Station 266, surface.

11. _Phractopelta hystrix_, Haeckel.

_Haliomma hystrix_, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 37, Taf. v. figs. 1, 2.

_Aspidomma hystrix_, Haeckel, 1862, Monogr. d. Radiol., p. 424.

Outer shell composed of twenty united plates, the meeting condyles of which are grown together. On the base of each radial spine four crossed circular aspinal spines of equal size. Sutural pores roundish, of about the same size. Radial spines conical, about as long as the radius of the shell.

_Dimensions._--Diameter of the outer shell 0.07, of the inner 0.024.

_Habitat._--Mediterranean (Nice), J. Müller, surface.

{855}Genus 367. _Pantopelta_,[407] n. gen.

_Definition._--#Phractopeltida# with twenty radial spines, each of which is protected by two free external apophyses.

The genus _Pantopelta_ differs from all other Phractopeltida in the development of free protecting apophyses on all twenty radial spines. Only a single specimen of this rare form was seen, and in this all twenty spines exhibited no marked differences in form and size, but were more or less irregularly developed.

1. _Pantopelta icosaspis_, n. sp. (Pl. 133, fig. 4).

Apophyses of all twenty radial spines with forked anastomosing branches, forming a more or less irregular cup-like fenestrated shield, pierced by a variable number of pores. Distance of the apophyses from the outer shell equal to half its radius. Pores of the outer shell irregular, roundish, four to six times as broad as those of the inner shell. Radial spines compressed, sword-shaped, longer than the radius of the shell.

_Dimensions._--Diameter of the outer shell 0.08, of the inner 0.03.

_Habitat._--Antarctic Ocean, Station 157, depth 1950 fathoms.

Genus 368. _Octopelta_,[408] n. gen.

_Definition._--#Phractopeltida# with twelve simple spines (four equatorial and eight polar), and with eight tropical spines protected by external free apophyses.

The genus _Octopelta_ differs from the other Phractopeltida in the possession of eight shields or pairs of free apophyses outside the outer lattice-shell; the spines bearing these apophyses are the eight tropical spines. The twelve other spines (eight polar and four equatorial) are quite simple, without apophyses.

1. _Octopelta cultella_, n. sp.

Apophyses of the eight tropical spines simple, compressed, knife-shaped, about as long as their distance from the outer shell. On the base of each spine (in the network of the outer shell) two orthogonal aspinal pores, two to three times as long as the other polygonal pores.

_Dimensions._--Diameter of the outer shell 0.08, of the inner 0.03.

_Habitat._--Tropical Atlantic, Station 338, surface.

{856}2. _Octopelta furcella_, n. sp.

Apophyses of the eight tropical spines forked, each with two parallel simple fork-branches, about as long as their distance from the outer shell. On the base of each spine (in the outer shell) two kidney-shaped aspinal pores, about twice as broad as the other irregular pores.

_Dimensions._--Diameter of the outer shell 0.1, of the inner 0.04.

_Habitat._--South Atlantic (off Tristan d'Acunha), Station 332, surface.

3. _Octopelta scutella_, n. sp. (Pl. 133, fig. 5).

Apophyses of the eight tropical spines crossed by a transverse beam, which is again crossed by two perpendicular branches; by union of these branches each tropical spine forms a square shield with four crossed pores and twelve to sixteen marginal spikes. On the base of each spine (in the surface of the outer shell) four crossed aspinal pores which correspond to those of the free shields; these are somewhat larger than the other pores.

_Dimensions._--Diameter of the outer shell 0.12, of the inner 0.06.

_Habitat._--Tropical Atlantic, Station 348, surface.

Genus 369. _Dorypelta_,[409] Haeckel, Prodromus, p. 369.

_Definition._--#Phractopeltida# with eight simple spines (four equatorial and four hydrotomical polar spines) and with twelve spines protected by external free apophyses (eight tropical and four geotomical polar spines).

The genus _Dorypelta_, the most common of all Phractopeltida which are protected by free apophyses, exhibits a very peculiar differentiation of its twenty radial spines. There are constantly eight simple spines and twelve spines with apophyses. The eight simple spines are the four equatorial spines and four polar spines placed in the hydrotomical median plane. The four other polar spines (placed in the geotomical meridian plane) and the eight tropical spines are protected by two opposite apophyses, which are now simple, now branched or shield-shaped. A similar differentiation occurs in no other Acanthophractida.

Subgenus 1. _Dorypeltarium_, Haeckel.

_Definition._--Free apophyses of the radial spines simple, not branched.

{857}1. _Dorypelta stauroptera_, n. sp.

Apophyses of the long compressed radial spines simple, conical, about as long as their distance from the shell. At the base of each spine (in the outer shell) two elliptical aspinal pores, two to three times as large as the other pores.

_Dimensions._--Diameter of the outer shell 0.1, of the inner 0.044.

_Habitat._--North Pacific, Station 238, surface.

2. _Dorypelta gladiata_, n. sp.

Apophyses of the long cylindrical radial spines simple, triangular, about half as long as their distance from the shell. At the base of each spine (in the outer shell) four crossed aspinal pores, the two opposite of which are much larger than the other two pores.

_Dimensions._--Diameter of the outer shell 0.09, of the inner 0.04.

_Habitat._--Central Pacific, Station 266, surface.

Subgenus 2. _Dorypeltidium_, Haeckel.

_Definition._--Free apophyses of the radial spines branched, with free (not anastomosing) branches.

3. _Dorypelta furcata_, n. sp.

Apophyses of the long compressed spines simply forked, each with two simple parallel fork-branches. At the base of each spine two elliptical aspinal pores, much larger than the other roundish pores.

_Dimensions._--Diameter of the outer shell 0.08, of the inner 0.04.

_Habitat._--Central Pacific, Station 274, surface.

4. _Dorypelta tetrodon_, n. sp.

Apophyses of the long compressed spines crossed by a transverse beam, which bears four simple parallel fork-branches or spikes (perpendicular to the beam), two larger medial and two smaller lateral. At the base of each spine four crossed aspinal pores of nearly equal size, little different from the other pores.

_Dimensions._--Diameter of the outer shell 0.09, of the inner 0.035.

_Habitat._--South Pacific, Station 284, surface.

5. _Dorypelta ramosa_, n. sp.

Apophyses of the long cylindrical spines crossed by a transverse beam, which bears four to six irregularly branched spikes or fork-branches, the medial of which are larger than the lateral. At {858}the base of each spine four crossed aspinal pores, two opposite of which are much larger than the two other pores.

_Dimensions._--Diameter of the outer shell 0.09, of the inner 0.04.

_Habitat._--South Pacific, Station 302, surface.

Subgenus 3. _Dorypeltonium_, Haeckel.

_Definition._--Free apophyses of the radial spines branched, and forming perforated shields by union of their anastomosing branches.

6. _Dorypelta lithoptera_, n. sp.

Apophyses of the long compressed radial spines with anastomosing branches; each spine bearing two free separated shields (each with two roundish aspinal pores). At the base of each spine (in the network of the outer shell) two elliptical aspinal pores, larger than the other pores.

_Dimensions._--Diameter of the outer shell 0.09, of the inner 0.03.

_Habitat._--North Pacific, Station 239, surface.

7. _Dorypelta tessaraspis_, n. sp. (Pl. 133, fig. 2).

Apophyses of the long cylindrical spines with anastomosing branches; each spine bearing a single free shield with four crossed aspinal pores of equal size (on the margin of the shield twelve to sixteen spikes). At the base of each spine (in the outer shell) four crossed aspinal pores, about as large as the other roundish pores.

_Dimensions._--Diameter of the outer shell 0.11, of the inner 0.05.

_Habitat._--Central Pacific, Station 263, surface.

8. _Dorypelta dodecaspis_, n. sp.

Apophyses of the long two-edged spines with anastomosing branches; each spine bearing a single free shield with six to eight parmal pores (four crossed aspinal pores alternating with four outer coronal pores), on the margin of each shield twelve to sixteen spikes. At the base of each spine (in the outer shell) four crossed aspinal pores, about as large as the other irregular pores.

_Dimensions._--Diameter of the outer shell 0.1, of the inner 0.04.

_Habitat._--North Pacific (off Japan), Station 235, surface.

Genus 370. _Stauropelta_,[410] Haeckel, 1881, Prodromus, p. 468.

_Definition._--#Phractopeltida# with four simple equatorial spines and sixteen spines protected by external free apophyses (eight tropical and eight polar spines).

{859}The genus _Stauropelta_ is distinguished from the other Phractopeltida by the possession of sixteen pairs of free apophyses (on the eight tropical and the eight polar spines); only the other four equatorial spines remain simple, without apophyses, and form a simple cross in the equatorial plane.

1. _Stauropelta cruciata_, n. sp. (Pl. 133, fig. 3).

Apophyses of the long polar and tropical spines crossed by a transverse beam, which is again crossed by two perpendicular branches parallel to the apophyses; branches with free ends, not united by concrescence. At the base of each spine (in the outer shell) two large elliptical aspinal pores, larger than the other irregular pores. Four equatorial spines simple, without apophyses, of the same size as the other sixteen spines.

_Dimensions._--Diameter of the outer shell 0.12, of the inner 0.05.

_Habitat._--Indian Ocean (Madagascar), Rabbe, surface.

2. _Stauropelta stauropora_, n. sp.

Apophyses of the long polar and tropical spines crossed by a transverse beam, which is again crossed by two perpendicular branches parallel to the apophyses; these branches are united by concrescence, and form a square shield with four crossed pores, the centre of which is pierced by the spine. At the base of each spine (in the outer shell) four crossed aspinal pores, corresponding to those of the shield, of about the same size as the other roundish pores. Four equatorial spines, simple, without apophyses, somewhat larger than the other sixteen spines.

_Dimensions._--Diameter of the outer shell 0.1, of the inner 0.04.

_Habitat._--Indian Ocean, Sunda-Archipelago, Singapore, Trebing, surface.

----

Suborder II. PRUNOPHRACTA.

_Definition._--Shell ellipsoidal, lenticular or diploconical, with radial beams of different size.

Family XLII. #BELONASPIDA#, n. fam. (Pl. 136, figs. 6-9; Pl. 139, figs. 8, 9).

_Definition._--ACANTHARIA with a simple ellipsoidal lattice-shell, composed of the branched apophyses of twenty radial spines meeting in its centre and disposed according to the Müllerian law of Icosacantha. Two opposite equatorial spines larger than the two others. Central capsule ellipsoidal, enclosed in the fenestrated shell.

The family #Belonaspida#, formerly united by me with the Dorataspida (in the Prodromus, 1881, p. 468), differs from it in the ellipsoidal form of the lattice-shell and {860}the enclosed central capsule. In the spherical Dorataspida, their ancestral family, all twenty radial spines are of equal size, whilst here in the Belonaspida two opposite spines are larger than the eighteen others. These two larger or principal spines are both equatorial spines, placed in the longitudinal or major axis of the ellipsoid, or the "hydrotomical axis" (compare above, p. 719). The two other equatorial spines are constantly smaller, and lie in the transverse or minor axis of the ellipsoid, or the "geotomical axis." The geometrical proportion of these two determining axes of the ellipsoidal shell is very variable (even in one and the same species), commonly 4 : 3 or 3 : 2, rarely 2 : 1, often only 5 : 4 or 6 : 5. All meridian planes, passing through the principal spines (or the longitudinal axis of the shell) are elliptical, and of equal size. All transverse planes, perpendicular to that axis, are circular; the largest of these circular parallel planes is the geotomical plane, which passes through the smaller equatorial spines and the spineless axis.

In the spherical Dorataspida the internal length of the radial spines (or the distance between the shell and the centre) is equal in all twenty spines. In the ellipsoidal Belonaspida this internal length is different, and commonly exhibits four different degrees; in the two principal spines it is of first rank, in the eight tropical spines of second rank, in the four (hydrotomical) polar spines of third rank, and in the six spines (four geotomical polar spines and two transverse equatorial spines) of fourth rank. These differences of the internal length become more important the more the hydrotomical axis is prolonged. Regarding all other qualities (in form, disposition, and mode of junction at the centre) the ellipsoidal Belonaspida do not differ from their ancestral group, the spherical Dorataspida (compare above, p. 802). In both families the pyramidal central bases of the twenty spines are commonly supported one upon another with their triangular neighbouring faces; but sometimes also here (particularly in _Phatnaspis_) the central bases are perfectly grown together. In this case also the sutures of the meeting branches of the apophyses are obliterated, whilst usually they remain open. Such forms, with spines and plates perfectly grown together, form a single piece of acanthin, and were formerly separated by me as a peculiar genus _Haliommatidium_ (Monogr. d. Radiol., 1862, p. 419). But as I now find this concrescence to be an accidental and inconstant peculiarity of some species, it no longer seems to me to be of generic importance.

The apophyses of the twenty radial spines, the branches of which compose the ellipsoidal lattice-shell, exhibit in all Belonaspida the same appearance as in the Diporaspida (and especially the Ceriaspida) among the spherical Dorataspida. Everywhere each radial spine gives off only two opposite primary apophyses, the fork-branches of which unite together and form a plate or shield with two aspinal pores (as in _Dorataspis_). Commonly the shell exhibits only these forty parmal pores, the other meshes between them being sutural pores. Only in one genus, _Phatnaspis_ (Pl. 136, {861}figs. 6-9), is this number multiplied; the two opposite primary apophyses are here crossed by numerous perpendicular lateral branches, and these are again united by secondary perpendicular ramules which are parallel to the apophyses themselves; therefore each plate here forms a rhombic shield pierced by very numerous (often more than one hundred) small quadrangular or circular pores. Only two of these numerous parmal pores are the primary aspinal pores (sometimes, as in Pl. 136, fig. 8, distinguished by their larger size); all others are secondary or coronal pores. Therefore _Phatnaspis_ repeats the characteristic formation of _Coscinaspis_, from which it differs in its ellipsoidal shell.

Moreover, the four other genera of the ellipsoidal Belonaspida correspond perfectly to certain genera of the spherical Dorataspida, and may be derived from these by hypertrophy or stronger development of two opposite equatorial spines. In _Thoracaspis_ and _Belonaspis_ (Pl. 139, figs. 8, 9) the surface of the shell-plates is without crests and dimples (in the former without, in the latter with accessory by-spines); they thus correspond to _Dorataspis_ and _Diporaspis_ among the Dorataspida. In two other genera the surface of the shell-plates bears a network of elevated crests, separating funnel-shaped dimples, in _Dictyaspis_ without, in _Coleaspis_ with by-spines; these correspond to _Ceriaspis_ and _Hystrichaspis_ among the Dorataspida. The small by-spines, covering the surface, exhibit the same forms as in the Dorataspida; but they are usually smaller, and less developed in the Belonaspida.

The twenty radial spines are commonly more or less compressed or two-edged, sometimes very flat, broad, and triangular (Pl. 139, figs. 8, 9). In some species (mainly of _Phatnaspis_) they are very long, thin, and needle-shaped (Monogr. d. Radiol., 1862, Taf. xxii. figs. 10-12). Rarely they are cylindrical, four-edged, or prismatic. The Belonaspida testify by this and other peculiarities to their near relation to the Diporaspida and Phractacanthida and their older origin from _Zygacantha_.

_The Central Capsule_ is in the Belonaspida ellipsoidal, and more or less prolonged in the hydrotomical or longitudinal axis of the shell. It is constantly smaller than the enveloping ellipsoidal shell, and separated from it by the calymma. Its structure and the shape of its nucleus are the same as in the nearly allied Dorataspida.

_Synopsis of the Genera of Belonaspida._

------------------------------------------------------------------------- I. Subfamily Coleaspida. Forty parmal pores (two aspinal pores on each plate, no coronal pores). ------------------------------------------------------------------------- Plates not dimpled, without { No by-spines, 371. _Thoracaspis_. prominent crests. { { With by-spines, 372. _Belonaspis_.

Plates dimpled, with a { No by-spines, 373. _Dictyaspis_. network of prominent { crests, { With by-spines, 374. _Coleaspis_. ------------------------------------------------------------------------- II. Subfamily Phatnaspida. Eighty to two thousand or more parmal pores (two aspinal pores on each plate, surrounded by two to one hundred or more coronal pores). ------------------------------------------------------------------------- No by-spines (plates not dimpled), 375. _Phatnaspis_.

{862}Genus 371. _Thoracaspis_,[411] Haeckel, 1862, Prodromus, p. 468.

_Definition._--#Belonaspida# with forty parmal pores (two on each plate), without dimples and crests, also without by-spines, therefore with smooth surface.

The genus _Thoracaspis_ is the simplest form among the Belonaspida, and repeats in this family the nearly allied genus _Dorataspis_ among the Dorataspida. It differs from this genus only in the characteristic prolongation of one equatorial axis, which effects an ellipsoidal transformation of the spherical central capsule and the enclosing lattice-shell.

1. _Thoracaspis ellipsoides_, n. sp.

Parmal pores large, elliptical, five or six times as large as the small circular sutural pores. Each plate surrounded by five or six sutural pores (a single one on each side). Spines compressed triangular, sword-like, two-edged; inner and outer half of nearly equal length.

_Dimensions._--Length of the ellipsoidal shell (or major axis) 0.15, breadth (or minor axis) 0.12; length of the spines 0.07, basal breadth 0.016.

_Habitat._--North Pacific, Station 253, surface.

2. _Thoracaspis nephropora_, n. sp.

Parmal pores large, kidney-shaped, three to four times as large as the roundish small sutural pores. Each plate surrounded by five or six sutural pores (a single one on each side). Spines in the inner longer part cylindrical, in the outer shorter part conical, not compressed.

_Dimensions._--Length of the shell 0.2, breadth 0.15; length of the spines 0.06, basal breadth 0.018.

_Habitat._--Central Pacific, Station 268, surface.

3. _Thoracaspis circopora_, n. sp.

Parmal pores circular, of the same size as the circular sutural pores. Each plate surrounded by five or six sutural pores (a single one on each side). Spines compressed, thin, linear, two-edged; outer part one and a half times as long as the inner.

_Dimensions._--Length of the shell 0.17, breadth 0.13; length of the spines 0.12, basal breadth 0.003.

_Habitat._--South Pacific, Station 288, surface.

4. _Thoracaspis bipennis_, n. sp. (Pl. 139, fig. 8).

Parmal pores elliptical, about twice as large as the circular sutural pores, which are of rather variable size. Each plate surrounded by eight to twelve sutural pores (commonly two on each side). {863}Spines compressed, triangular, gradually tapering towards both ends; outer half a little longer, and much broader than the inner.

_Dimensions._--Length of the shell 0.14, breadth 0.12; length of the spines 0.08, basal breadth 0.025.

_Habitat._--Central Pacific, Station 274, surface.

Genus 372. _Belonaspis_,[412] Haeckel, 1862, Prodromus, p. 468.

_Definition._--#Belonaspida# with forty parmal pores (two on each plate), without dimples and crests, but with numerous by-spines on the surface.

The genus _Belonaspis_ differs from its ancestral genus _Thoracaspis_ only in the possession of numerous superficial by-spines, and bears therefore to it the same relation as _Diporaspis_ does to _Dorataspis_. The two latter differ from the two former in the spherical form of the central capsule and the enclosing shell, which here becomes ellipsoidal.

1. _Belonaspis pandanus_, n. sp.

Parmal pores elliptical, three or four times as large as the circular sutural pores. Each plate surrounded by five or six sutural pores (a single one on each side). Spines compressed, triangular; outer part half as long as the inner, and twice as long as the numerous, simple, bristle-shaped by-spines.

_Dimensions._--Length of the ellipsoidal shell (or major axis) 0.12, breadth (or minor axis) 0.1; length of the spines 0.03, basal breadth 0.02.

_Habitat._--South Pacific, Station 295, surface.

2. _Belonaspis furcata_, n. sp.

Parmal pores elliptical, twice as broad as the circular sutural pores. Each plate surrounded by five or six sutural pores (a single one on each side). Spines compressed, linear, very thin; outer part longer than the inner. By-spines very numerous, half as long as the radius, furcate, with divergent fork-branches.

_Dimensions._--Length of the shell 0.1, breadth 0.08; length of the spines 0.12, breadth 0.003.

_Habitat._--Indian Ocean (Cocos Islands), Rabbe, surface.

3. _Belonaspis datura_, n. sp. (Pl. 139, fig. 9).

Parmal pores elliptical, three or four times as large as the circular sutural pores. Each plate surrounded by ten or twelve sutural pores (two on each side). Spines triangular, two-edged, about {864}as long as the radius of the shell; gradually tapering from its surface towards both ends. By-spines very short and numerous, simple.

_Dimensions._--Length of the shell 0.13, breadth 0.11; length of the spines 0.08, basal breadth 0.025.

_Habitat._--Central Pacific, Station 271, surface.

4. _Belonaspis lanceolata_, n. sp.

Parmal pores elliptical, six or eight times as large as the small circular sutural pores. Each plate surrounded by ten to twelve sutural pores (two on each side). Spines lanceolate, flat, in the distal part needle-shaped, about as long as the diameter of the shell. By-spines very numerous, zigzag, half as long as the shell-radius.

_Dimensions._--Length of the shell 0.15 breadth 0.13; length of the spines 0.14, basal breadth 0.03; length of the by-spines 0.04.

_Habitat._--North Pacific, Station 235, surface.

5. _Belonaspis conifera_, n. sp.

Parmal pores kidney-shaped, three or four times as large as the small circular pores. Each plate surrounded by ten to twelve sutural pores (two on each side). Spines very thick, half as long in the outer conical part as in the inner cylindrical part. By-spines very short, conical.

_Dimensions._--Length of the shell 0.2, breadth 0.16; length of the spines 0.05, basal breadth 0.03.

_Habitat._--Central Pacific, Station 267, surface.

6. _Belonaspis multiforis_, n. sp.

Parmal pores circular, of the same size as the circular sutural pores. Each plate surrounded by fifteen to eighteen sutural pores (three on each side). Spines compressed, about as long as the radius. By-spines very numerous, zigzag, half as long as the radius.

_Dimensions._--Length of the shell 0.22, breadth 0.18; length of the spines 0.12, basal breadth 0.012; length of the by-spines 0.06.

_Habitat._--Equatorial Atlantic, Station 347, surface.

Genus 373. _Dictyaspis_,[413] n. gen.

_Definition._--#Belonaspida# with forty parmal pores (two on each plate), without by-spines, but with a network of prominent crests on the dimply surface.

The genus _Dictyaspis_ repeats among the Belonaspida the characteristic structure of _Ceriaspis_ (among the Dorataspida), by the development of prominent crests forming a {865}network with dimples on the outer surface of the shields. Either all the dimples or only a part of them are pierced by a pore. The forty aspinal pores are united in pairs in twenty larger dimples. The shell is usually very thick-walled and non-transparent.

1. _Dictyaspis solidissima_, Haeckel.

_Dorataspis solidissima_, Haeckel, 1862, Monogr. d. Radiol., p. 416, Taf. xxii. figs. 6-9.

Surface of the shell with seventy to eighty funnel-shaped dimples, each of which is perforated at the base by one or two small meshes; twenty larger dimples in the centre of the plates (each with two elliptical aspinal pores), and fifty to sixty smaller sutural dimples between them (each with a single circular pore). All pores of nearly the same size. No blind dimples. Outer conical part of the thick radial spines of the same length as the inner cylindrical part. Radius of the shell four times as large as the thickness of its wall.

_Dimensions._--Length of the shell 0.12, breadth 0.1; length of the spines 0.06, basal breadth 0.012.

_Habitat._--Mediterranean (Messina), surface.

2. _Dictyaspis favosa_, n. sp.

Surface of the shell with one hundred and seventy to one hundred and ninety deep funnel-shaped dimples, seventy to eighty of which are perforated, the others blind; among the former each of the fifty to sixty smaller contains a single sutural pore, each of the twenty larger a couple of aspinal pores. All pores of nearly the same size. Outer part of the compressed two-edged spines triangular, half as long as the inner part. Radius of the shell six times as large as the thickness of its wall. (Differs from _Ceriaspis favosa_, Pl. 138, fig. 6, mainly in the ellipsoidal form of the shell and the different size and form of the spines.)

_Dimensions._--Length of the shell 0.16, breadth 0.13; length of the spines 0.04, basal breadth 0.025.

_Habitat._--Central Pacific, Station 265, surface.

3. _Dictyaspis compacta_, n. sp.

Surface of the shell with one hundred and seventy to one hundred and ninety deep funnel-shaped dimples, seventy to eighty of which are perforated, the others blind; among the former each of fifty to sixty each contain a single sutural pore, twenty each a couple of aspinal pores. All dimples nearly of the same size, very deep. Outer part of the compressed sword-like spines somewhat longer than the inner part. Radius of the dark shell only twice as large as the thickness of its compact wall.

_Dimensions._--Length of the shell 0.18, breadth 0.15; length of the spines 0.12, basal breadth 0.02.

_Habitat._--Central Pacific, Station 274, surface.

{866}Genus 374. _Coleaspis_,[414] Haeckel, 1881, Prodromus, p. 468.

_Definition._--#Belonaspida# with forty parmal pores (two on each plate), with numerous by-spines and with a network of prominent crests on the dimpled surface.

The genus _Coleaspis_ differs from its ancestral genus _Dictyaspis_ in the development of numerous by-spines, and bears therefore among the ellipsoidal Belonaspida the same relation to it as _Hystrichaspis_ does to _Coscinaspis_ among the spherical Dorataspida. If the four equatorial spines in _Coleaspis_ become different in pairs, it passes over into _Hexalaspis_. The shell is usually very dark and thick-walled.

1. _Coleaspis coronata_, n. sp.

All twenty spines of nearly equal size and form, about as long as the radius of the shell, compressed, sword-like, two-edged; both equatorial spines of the hydrotomical axis little longer than the eighteen others. Crests between the dimples of the shell-surface dentated, forming around the basal half of each spine a cylindrical sheath with a dentated, crown-like mouth, the teeth of which are prolonged into simple by-spines. (Similar to _Hexaconus coronatus_, Pl. 139, fig. 5, but differing in the nearly equal size of the spines and their sheaths, and in the longer by-spines.)

_Dimensions._--Major axis of the shell 0.2, minor 0.17; length of the spines 0.12, basal breadth 0.02.

_Habitat._--Central Pacific, Station 266, surface.

2. _Coleaspis vaginata_, n. sp. (Pl. 140, fig. 13).

All twenty spines of nearly equal size and form, nearly as long as the diameter of the shell, conical; both equatorial spines of the hydrotomical axis about one-third longer than the eighteen others. Crests between the dimples of the shell-surface serrated, forming around the basal half of each spine a conical truncate sheath with crested surface and serrated mouth, the teeth of which are prolonged into short by-spines. (Similar to _Hexaconus vaginatus_, Pl. 139, fig. 7, but differing in the nearly equal size of all the spines and in the double thickness of the shell-wall.)

_Dimensions._--Major axis of the shell 0.12, minor 0.1, length of the spines 0.08, basal breadth 0.01.

_Habitat._--North Pacific, Station 253, surface.

3. _Coleaspis obscura_, n. sp.

All twenty spines of nearly equal size and form, little longer than their large cylindrical sheaths, which are nearly as long as the radius of the shell, and armed on the truncated mouth with strong triangular by-spines, both equatorial spines of the hydrotomical axis one and a half times as long as the eighteen others. Shell very dark and thick walled, quite opaque.

{867}_Dimensions._--Major axis of the shell 0.1, minor 0.08; length of the spines 0.06, of their sheaths 0.04.

_Habitat._--Arctic Ocean, Greenland, Koch, surface.

4. _Coleaspis occulta_, n. sp.

All twenty spines of nearly equal size and form, quite concealed in their long cylindrical sheaths, which are somewhat longer than the radius of the shell, and armed on the truncated mouth with acute simple teeth; each sheath deeply sulcated, apparently resulting from the concrescence of numerous parallel leaf-shaped by-spines. Small shell very dark and thick-walled, quite opaque.

_Dimensions._--Major axis of the shell 0.08, minor 0.06; length of the spines and their sheaths 0.05 to 0.06.

_Habitat._--Antarctic Ocean (off Kerguelen), Station 159, surface.

Subgenus 2. _Coleaspidium_, Haeckel.

_Definition._--Both equatorial spines of the hydrotomical axis much larger and of peculiar form, different from the eighteen other spines.

5. _Coleaspis amphilonche_, n. sp.

Both equatorial spines of the hydrotomical axis much longer than the eighteen others, and of very different form; one and a half times as long as the diameter of the shell, prismatic, with six prominent edges, pyramidal at the distal point. The eighteen other spines triangular, compressed, two-edged, scarcely as long as the radius of the thick-walled shell. Pores of the shell irregular polygonal, separated by ciliated crests, which bear simple by-spines (one-third as long as the radius).

_Dimensions._--Major axis of the shell 0.15, minor 0.12; length of the two larger spines 0.22, of the eighteen smaller 0.06 to 0.08; basal breadth of the former 0.03, of the latter 0.008.

_Habitat._--South Atlantic, Station 341, surface.

6. _Coleaspis hydrotomica_, n. sp. (Pl. 140, fig. 14).

Both equatorial spines of the hydrotomical axis much larger than the eighteen others, and of very different form; about as long as the diameter of the shell, in the basal half four-sided pyramidal, with four thick prominent edges, in the middle part constricted, in the distal half lanceolate, two-edged. Both equatorial spines of the geotomical axis of similar form, but much smaller, scarcely one-third as long. The sixteen other spines sword-like, thin, two-edged, about as long as the radius of the thick-walled shell. Pores of the shell irregular roundish, separated by high dentated crests, which bears zigzag by-spines (half as long as the radius).

_Dimensions._--Major axis of the shell 0.12, minor axis 0.1; length of the two larger spines 0.11, of the eighteen others 0.04 to 0.06; basal breadth of the former 0.04, of the latter 0.01.

_Habitat._--Cape of Good Hope, Station 143, surface.

{868}Genus 375. _Phatnaspis_,[415] Haeckel, 1881, Prodromus, p. 468

_Definition._--#Belonaspida# with eighty to two thousand or more parmal pores (four to one hundred or more on each plate), without by-spines on the surface.

The genus _Phatnaspis_ corresponds to the spherical _Coscinaspis_ among the Dorataspida, and differs from the other Belonaspida in the great number of the parmal pores; whilst the four other preceding genera exhibit only two opposite aspinal pores in the centre of each plate, in this there are constantly numerous coronal pores in addition to these, and the plates always possess the characteristic form of a wainscotted or panelled work, with quadrangular meshes. The number of these parmal pores amounts in each plate to from ten to twenty, often one hundred and twenty or more; therefore the number of parmal pores in the whole shell amounts to two thousand or more. Sometimes the pores are circular, but in this case too they are surrounded by quadrangular frames. The quadrangles are sometimes quite regular squares, sometimes more or less irregular. The thin and fragile bars between the quadrangular pores form in each plate two peculiar systems of parallel crests, which cross at right angles. Commonly the parallel crests of one system (parallel to the major diameter of the compressed radial spines) are equidistant, and pierce from one edge of the plate to the opposite, whilst the parallel crests of the other system (parallel to the minor diameter of the spines) are interrupted and at different distances (Pl. 136, fig. 9); but in other species both crossed systems are quite regular. In each plate there is one primary diagonal rib (often stronger than the parallel crests) which connects the two opposite corners of the rhomboidal plate. We can distinguish in this genus three different subgenera: A. in _Phatnasparium_ the primary diagonal rib arises from both flat sides of the compressed sword-like, radial spines; B. in _Phatnasplenium_ from both sharp edges of them; C. in _Phatnaspidium_ two crossed diagonal ribs arise from four edges of the spines (combination of A and B). Therefore in the first subgenus (A) two primary aspinal pores are placed opposite on the sharp edges of the spines, but in the second (B) inversely on their flat sides; in the third (C) there are apparently four primary aspinal pores, which are probably derived from B or A by division of the two pores.

Subgenus 1. _Phatnasparium_, Haeckel.

_Definition._--In the centre of each rhomboidal plate two primary aspinal pores, opposite on both edges of the compressed spines, from both flat sides of which the primary diagonal crest arises.

{869}1. _Phatnaspis lacunaria_, n. sp. (Pl. 136, fig. 9).

Parmal pores irregular quadrangular, of unequal size and form, ten to twelve on each side of the primary diagonal rib, which arises from both flat sides of the two-edged spines; two primary aspinal pores opposite on both edges of the latter. Spines much compressed, sword-like, their outer half shorter than the inner.

_Dimensions._--Length of the shell 0.21 to 0.23, breadth 0.18 to 0.2; basal breadth of the spines 0.01.

_Habitat._--Central Pacific, Station 268, surface.

2. _Phatnaspis ensiformis_, n. sp.

Parmal pores irregular quadrangular, of unequal size and form, six to eight on each side of the primary diagonal rib, which arises from both flat sides of the two-edged spines; two primary aspinal pores opposite on the two edges of the latter. Spines very broad, strongly compressed, sword-like, their outer half larger than the inner.

_Dimensions._--Length of the shell 0.16, breadth 0.11; basal breadth of the spines 0.02.

_Habitat._--Tropical Atlantic, Station 348, surface.

3. _Phatnaspis loculata_, n. sp.

Parmal pores regular quadrangular, of nearly equal size and form, twelve to sixteen on each side of the primary diagonal rib, which arises from both flat sides of the two-edged spines; two primary aspinal pores on the two edges of the latter. Spines linear, compressed, very long and thin, their outer half three to four times as long as the inner.

_Dimensions._--Length of the shell 0.24, breadth 0.18; breadth of the spines 0.004.

_Habitat._--North Atlantic, Station 354, surface.

4. _Phatnaspis fenestrata_, Haeckel.

_Haliommatidium fenestratum_, Haeckel, 1862, Monogr. d. Radiol., p. 421.

Parmal pores regular quadrangular, of nearly equal size and form, six to eight on each side of the primary diagonal rib, which arises from both flat sides of the two-edged spines; two primary aspinal pores on the two edges of the latter. Spines linear, little compressed, or nearly needle-shaped, very long and thin, their outer half five to ten times as long as the inner.

_Dimensions._--Length of the shell 0.11 to 0.12, breadth 0.07 to 0.08; breadth of the spines 0.002.

_Habitat._--Mediterranean (Messina), surface.

5. _Phatnaspis cristata_, n. sp. (Pl. 136, fig. 6).

Parmal pores circular, of very different size, separated by high square crests, ten to twelve on each side of the high, comb-like, primary diagonal rib, which arises from both flat sides of the {870}twoedged spines; two primary aspinal pores on the two edges of the latter. Each circular pore is surrounded by a square frame. Spines sword-like, strongly compressed, their outer part longer than the inner.

_Dimensions._--Length of the shell 0.2 to 0.22, breadth 0.16 to 0.18; basal breadth of the spines 0.01.

_Habitat._--North Pacific, Station 254, surface.

6. _Phatnaspis coscinoides_, n. sp.

Parmal pores circular, regular, all of nearly equal size, twelve to sixteen on each side of the primary diagonal rib, which arises from both flat sides of the two-edged spines; two primary pores on the two edges of the latter. Spines linear, little compressed, their outer part much longer than the inner.

_Dimensions._--Length of the shell 0.18, breadth 0.15; breadth of the spines 0.006.

_Habitat._--South Atlantic, Station 325, surface.

Subgenus 2. _Phatnasplenium_, Haeckel.

_Definition._--In the centre of each rhomboidal plate two primary aspinal pores, opposite on the two flat sides of the compressed spines, from the two edges of which the primary diagonal crest arises.

7. _Phatnaspis orthopora_, n. sp.

Parmal pores irregular quadrangular, of unequal size and form, four to six on each side of the primary diagonal rib, which arises from both edges of the compressed spines; two larger primary aspinal pores opposite on the two flat sides of the latter. Spines very thin and long, linear, their outer half three to four times as long as the inner.

_Dimensions._--Length of the shell 0.08, breadth 0.06; breadth of the spines 0.003.

_Habitat._--North Atlantic, Station 353, surface.

8. _Phatnaspis polypora_, n. sp.

Parmal pores irregular polygonal, of very unequal size and form, sixteen to twenty on each side of the primary diagonal rib, which arises from both edges of the compressed spines; two very large, lanceolate, primary aspinal pores opposite on the two flat sides of the latter. Spines very thin, linear, on the outside of the shell rudimentary. (This remarkable species somewhat resembles _Coscinaspis polypora_, Pl. 136, fig. 8.)

_Dimensions._--Length of the shell 0.32, breadth 0.24; breadth of the spines 0.002.

_Habitat._--South Atlantic, Station 332, surface.

{871}9. _Phatnaspis quadratura_, n. sp.

Parmal pores regular, square, all of nearly equal size and form, ten to twelve on each side of the primary diagonal rib, which arises from both edges of the compressed spines; two primary aspinal pores opposite on the two flat sides of the latter, not different from the other pores. Spines sword-like, their outer part about as long as the inner.

_Dimensions._--Length of the shell 0.2, breadth 0.16; basal breadth of the spines 0.004.

_Habitat._--Central Pacific, Station 274, surface.

10. _Phatnaspis tabulata_, Haeckel.

_Haliomma tabulatum_, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 37, Taf. v. figs. 5-8.

_Haliomma tabulatum_, Haeckel, 1862, Monogr. d. Radiol., p. 429.

Parmal pores regular, circular, with square frames, all of nearly equal size, eight to ten on each side of the primary diagonal rib, which arises from both edges of the compressed spines; two primary aspinal pores opposite on the flat sides of the latter. Spines sword-like, short, scarcely half as long as the radius of the shell, their central ends are thickened and cause by their union the deceptive appearance of an enclosed "medullary shell."

_Dimensions._--Length of the shell 0.12 to 0.15, breadth 0.1 to 0.12; breadth of the spines 0.006.

_Habitat._--Mediterranean; Nice, Müller; Portofino, near Genoa, Haeckel, surface.

Subgenus 3. _Phatnaspidium_, Haeckel.

_Definition._--In the centre of each rhomboidal plate four primary aspinal spines, forming a regular cross, the centre of which receives the cylindrical or four-sided prismatic spine.

11. _Phatnaspis haliommidium_, n. sp. (Pl. 136, fig. 7).

Parmal pores irregular quadrangular, of unequal size and form, eight to ten on each side of the crossed diagonal ribs, which arise at right angles from the four edges of the prismatic spines; four primary aspinal pores not different from the others. Outer part of the strong spines scarcely longer than the inner. (Resembling _Icosaspis tabulata_, Pl. 136, fig. 2, which, however, is distinguished by the spherical shell and the larger pores.)

_Dimensions._--Length of the shell 0.22, breadth 0.17; breadth of the spines 0.016.

_Habitat._--North Pacific, Station 244, surface.

12. _Phatnaspis mülleri_, n. sp.

_Haliommatidium mülleri_, Haeckel, 1862, Monogr. A. Radiol, p. 419, pl. xiii. figs. 10-12.

Parmal pores regular, square, all of nearly equal size and form, twelve to sixteen on each side of the crossed diagonal ribs, which arise at right angles from the needle-shaped spines; the four {872}primary aspinal pores not different from the others. Spines very thin and long, cylindrical; four to six times longer in the outer than in the inner part.

_Dimensions._--Length of the shell 0.24, breadth 0.16; breadth of the spines 0.002.

_Habitat._--Mediterranean (Messina), surface.

Family XLIII. #HEXALASPIDA#, n. fam. (Pl. 139).

_Definition._--ACANTHARIA with a simple discoidal or lenticular lattice-shell, composed of the branched apophyses of twenty radial spines meeting in the centre and disposed according to the Müllerian law of Icosacantha. Six larger spines in the hydrotomical plane, prominent on the margin of the circular or elliptical biconvex lens. Fourteen other spines much smaller or rudimentary. Central capsule biconvex lenticular, enclosed in the fenestrated shell.

The family #Hexalaspida# represents a new small, but very interesting group of Acanthophracta, which differs from all others in the lentelliptical or triaxial form of the lenticular lattice-shell, the margin of which bears six larger spines placed in the hydrotomical plane (compare above, p. 719). They may therefore be characterised shortly as "_Acanthophracta lentelliptica_," with three different dimensive axes and six larger marginal spines. A closer comparison with the other ACANTHARIA leaves no doubt that the Hexalaspida must be derived from the Belonaspida by stronger development of six radial spines placed in the hydrotomical plane, namely, two equatorial and four associated polar spines; whilst the six spines of the geotomical plane (perpendicular to the former) are much smaller; the eight tropical spines are intermediate in size between the former and the latter.

The geometrical fundamental form of the Hexalaspida (of the central capsule as well as of the enclosing shell) is therefore lentelliptical, with three different dimensive axes, and they exhibit among the ACANTHARIA a relation to the spherical Dorataspida and the ellipsoidal Belonaspida similar to that which the lentelliptical #Larcoidea# exhibit to the spherical #Sphæroidea# and the ellipsoidal #Prunoidea# among the #Sphærellaria# (compare above, p. 599). The largest of the three dimensive axes (which are perpendicular to one another) is here the hydrotomical axis, the shortest, on the contrary, the geotomical axis; the intermediate in size being the spineless axis. The development of the whole body is strongest in the hydrotomical meridian plane, in which the six principal spines are placed; it is weakest in the geotomical plane, in which the six smallest spines are placed; the eight tropical spines are intermediate in size between the others. This peculiar development is illustrated by the figures of Pl. 139, where the four equatorial spines are everywhere marked by _c_, the eight tropical spines by _b_ and _d_, the eight polar spines by _a_ and _e_.

{873}Rarely the six hydrotomical or principal spines are of equal size, and thus the margin of the shell may be quite circular or regularly hexagonal (Pl. 139, figs. 1-3); the two equatorial spines of the hydrotomical plane are usually larger than its four polar spines, and thus the margin of the shell becomes more or less elliptical (Pl. 139, figs. 4-7). Usually (almost constantly) these six larger spines are more or less compressed, triangular, often very broad and flat; their two edges lie in the hydrotomical plane. Their two flat surfaces are often furrowed, with longitudinal ribs or crests converging towards the simple apex of the spines.

The fourteen smaller spines are regularly disposed according to the Müllerian law of Icosacantha on both convex sides of the lenticular shell; they are not only smaller than the six principal spines, but often also of different form, much thinner and shorter, sometimes needle-shaped. In the genera _Hexonaspis_ and _Hexacolpus_ (Pl. 139, figs. 1, 2) only their inner part (inside of the shell) is developed, whilst their outer part is quite rudimentary and not prominent on the surface. Therefore these genera appear to possess only six marginal spines externally.

_The Lenticular Shell_ itself offers in the Hexalaspida great difficulties in the way of accurate study, as its wall is constantly very thick and dark, often quite opaque and non-transparent. However, prolonged accurate researches have convinced me that its structure is essentially the same as in the Belonaspida and especially in the genera _Dictyaspis_ and _Coleaspis_. As in these latter the twenty plates of the shell bear high crests or combs on the outer surface, and by these funnel-shaped dimples are separated. The network of these crests is more or less regular (Pl. 139, figs. 1-7). Around the base of each radial spine the shell is usually elevated in the form of a conical or cylindrical sheath; the crests are prolonged into the sheaths as longitudinal ribs, parallel to the spine or convergent towards its apex. Whilst in _Hexalaspis_ and _Hexonaspis_ these basal sheaths are not at all or but little prominent (Pl. 139, fig. 2; Pl. 140, fig. 16), in _Hexaconus_ and _Hexacolpus_ they envelop the basal half (or even more) of the spines, and very often the circular or elliptical free distal edge of the sheath is elegantly denticulated or serrated (Pl. 139, figs. 1, 3-7; pl. 140, figs. 9-16).

_The Pores_ of the shell exhibit in the Hexalaspida the same shape as in the majority of the Belonaspida. Each spine bears only two broad opposite apophyses, the fork-branches of which unite to form a polygonal shield with two pores. The number of parmal pores is constantly (?) forty, as each plate possesses only two primary aspinal pores; there are no secondary or coronal pores. The numerous (between fifty and one hundred, rarely more) smaller pores between the forty parmal pores are probably always sutural pores; however, their number and position is very difficult to determine, on account of the high protecting crests; the majority of the funnel-shaped dimples between the latter seem to be blind, not perforated. Sometimes all the dimples, except the twenty spinal ones, seem to be blind and the sutural pores appear {874}to have disappeared completely, so that there remain only twenty aspinal pores (Pl. 139, fig. 4).

The internal cavity of the shell in all Hexalaspida is very small, on account of the thickness of the massive wall; the latter is often greater than the diameter of the cavity. Setting aside this disproportion, the space of the cavity is further much reduced by the internal parts of the thick radial spines, which are united in the centre by their pyramidal bases (Pl. 140, fig. 15). Usually the twenty bases seem to remain free (supported one upon another by means of their triangular faces); but sometimes they seem to grow together perfectly and to form a single central star of acanthin. In some species, too, the sutures of the meeting branches of the apophyses of neighbouring spines seem to grow together, so that the whole shell exhibits a single piece of acanthin.

_The Central Capsule_ of the Hexalaspida is therefore very small and seems to fill up the greatest part of the shell-cavity. Its form is constantly more or less lenticular, sometimes lentelliptical. On account of the opacity of the shell I could not make out its shape more closely.

_Synopsis of the Genera of Hexalaspida._

All twenty spines externally } Sheaths of the spines developed, prominent on } not prominent, 376. _Hexalaspis_. the surface of the } lenticular shell. } Sheaths of the spines } prominent, 377. _Hexaconus_.

Only six spines (the } hydrotomical spines) } Sheaths of the spines externally developed and } not prominent, 378. _Hexonaspis_. prominent on the margin } of the disk; the other } Sheaths of the spines fourteen spines not } prominent, 379. _Hexacolpus_. prominent. }

Genus 376. _Hexalaspis_,[416] n. gen.

_Definition._--#Hexalaspida# with twenty prominent radial spines, which are not surrounded by prominent sheaths; the six hydrotomical spines much larger than the fourteen others.

The genus _Hexalaspis_ is the simplest form among the Hexalaspida, and may be derived directly from _Dictyaspis_ among the Belonaspida, by stronger development of the six hydrotomical spines. As in the following genus _Hexaconus_ all twenty spines are prominent externally.

Subgenus 1. _Hexalasparium_, Haeckel.

_Definition._--Six hydrotomical spines of equal size.

{875}1. _Hexalaspis heliodiscus_, n. sp. (Pl. 139, fig. 2).

All six hydrotomical spines of nearly equal size (or sometimes the two equatorial a little larger than the four polar spines), isosceles triangular, compressed, smooth; about as long as the radius of the shell, and half as broad at the base. The fourteen other spines very small, also triangular and compressed, but little prominent on the two convex sides of the lenticular shell.

_Dimensions._--Diameter of the shell 0.11; length of the six hydrotomical spines 0.05, basal breadth 0.03.

_Habitat._--Central Pacific, Station 271 to 274, surface.

2. _Hexalaspis stellata_, n. sp.

All six hydrotomical spines of nearly equal size, lanceolate compressed, with two longitudinal furrows on each flat side, about as long as the diameter of the shell, and one-fourth as broad at the base. The fourteen other spines very thin, also compressed, half as long and only one-fourth as broad as the six large spines.

_Dimensions._--Diameter of the shell 0.14; length of the six hydrotomical spines 0.13, basal breadth 0.035.

_Habitat._--South Pacific, Station 284, surface.

Subgenus 2. _Hexalaspidium_, Haeckel.

_Definition._--Six hydrotomical spines of unequal size, two opposite (equatorial) much larger than the four other (polar) spines.

3. _Hexalaspis sexalata_, n. sp.

Six hydrotomical spines of unequal size; the two equatorial spines about as long as the shell-radius and twice as long as the four polar spines, which are isosceles triangular. The fourteen other spines are only half as long and one-fourth as broad as the latter, little prominent. (Resembles _Hexonaspis hastata_, Pl. 140, fig. 16, which is distinguishable by the furrows on the six spines and by the total absence of the fourteen external rudimentary spines.)

_Dimensions._--Diameter of the shell 0.15; length of the two equatorial spines 0.08, of the four polar spines 0.04, of the fourteen other spines 0.02.

_Habitat._--North Pacific, Station 240, surface.

4. _Hexalaspis hexalastrum_, n. sp.

Six hydrotomical spines of unequal size; the two equatorial spines somewhat longer than the diameter of the shell and three times as long as the four polar spines, all six triangular, smooth, of the same basal breadth (equal to half the radius). The fourteen other spines very thin, conical at the base, nearly as long as the radius.

{876}_Dimensions._--Diameter of the shell 0.21; length of the two equatorial spines 0.24, of the eighteen others 0.08 to 0.1; basal breadth of the six larger spines 0.05, of the fourteen others 0.01.

_Habitat._--Western Tropical Pacific, Station 224, surface.

5. _Hexalaspis hexaglypha_, n. sp.

Six hydrotomical spines of unequal size; the two equatorial very large, six-sided prismatic, twice as long as the diameter of the shell and four times as long as the four pyramidal polar spines; each of these six spines with six deep furrows between the six prominent edges. The fourteen other spines very thin, compressed, two-edged, about as long as the radius of the shell.

_Dimensions._--Diameter of the shell 0.11; length of the two equatorial spines 0.2, of the eighteen others 0.04 to 0.06; basal breadth of the six larger spines 0.03, of the fourteen others 0.01.

_Habitat._--Tropical Atlantic, Station 352, surface.

Genus 377. _Hexaconus_,[417] n. gen.

_Definition._--#Hexalaspida# with twenty prominent radial spines, which are surrounded at the base by prominent sheaths; the six hydrotomical spines much larger than the fourteen others.

The genus _Hexaconus_ differs from the preceding _Hexalaspis_ in the development of conical or cylindrical sheaths surrounding the basal parts of the radial spines; these sheaths are developed sometimes around all twenty spines, sometimes only around the six larger hydrotomical spines.

Subgenus 1. _Hexaconarium_, Haeckel.

_Definition._--Six hydrotomical spines of equal size.

1. _Hexaconus ciliatus_, n. sp. (Pl. 139, fig. 3).

All six hydrotomical spines of nearly equal size, pyramidal, with six prominent edges, somewhat longer than the radius of the shell. Sheaths sulcated, finely ciliated at the mouth, twice as broad as long and only one-fourth as long as the spines. The fourteen smaller spines very thin, bristle-shaped, shorter than the radius of the shell.

_Dimensions._--Diameter of the shell 0.16; length of the six hydrotomical spines 0.11; basal breadth 0.03.

_Habitat._--Central Pacific, Station 270, surface.

{877}2. _Hexaconus coronatus_, n. sp. (Pl. 139, fig. 5).

All six hydrotomical spines of equal size, conical, somewhat compressed, with two prominent edges, scarcely as long as the radius of the shell. Sheaths crested, strongly dentated on the mouth, three times as broad as long and only one-sixth as long as the spines. Fourteen smaller spines about half as large as the six principal spines, of the same form, but without coronated sheaths.

_Dimensions._--Diameter of the shell 0.2; length of the six hydrotomical spines 0.1; basal breadth 0.02.

_Habitat._--North Pacific, Station 253, surface.

3. _Hexaconus velatus_, n. sp. (Pl. 139, fig. 6).

All six hydrotomical spines of equal size, conical, somewhat compressed, shorter than the radius of the shell. Sheaths very large, truncated conical, enveloping the spines almost entirely, with crested wall, only half as broad at the constricted mouth as at the base. The fourteen smaller spines about half as large as the six principal spines, of the same form, but without large sheaths.

_Dimensions._--Diameter of the shell 0.12; length of the six hydrotomical spines 0.05; basal breadth 0.01.

_Habitat._--North Atlantic, Station 354, surface.

Subgenus 2. _Hexaconidium_, Haeckel.

_Definition._--Six hydrotomical spines of unequal size, two opposite (equatorial) much larger than the four other (polar) spines.

4. _Hexaconus serratus_, n. sp. (Pl. 139, fig. 4).

Six hydrotomical spines of unequal size, the two equatorial being as long as the radius of the shell and one and a half times as large as the four polar; all of the same form, triangular, compressed, with six prominent edges. Sheaths cylindrical, half as long as the spines, with prominent crests, and with strong serrated teeth at the distal mouth. The fourteen smaller spines scarcely one-fourth or one-sixth as large as the six principal spines, without prominent sheaths.

_Dimensions._--Diameter of the shell 0.2; length of the equatorial spines 0.1, basal breadth 0.05; length and breadth of the sheaths 0.05.

_Habitat._--South Pacific, Station 288, surface.

5. _Hexaconus vaginatus_, n. sp. (Pl. 139, fig. 7).

Six hydrotomical spines of unequal size; the two equatorial very stout, pyramidal, six-edged, nearly as long as the diameter of the shell, and on the base three to four times as broad as the eighteen other spines, which are much thinner, all nearly of equal length, and two-edged. All {878}twenty spines are provided with prominent basal sheaths, which are truncate conical, sulcate, and dentate on the narrowed distal mouth. The sheaths of the six hydrotomical spines are twice to three times as large as those of the fourteen smaller spines.

_Dimensions._--Diameter of the shell 0.15; length of the spines 0.12; basal breadth of the equatorial spines 0.04, of the other spines 0.02; length of the hydrotomical sheaths 0.05, of the other sheaths 0.02.

_Habitat._--Central Pacific, Station 274, surface.

6. _Hexaconus echinatus_, n. sp. (Pl. 140, fig. 12).

Six hydrotomical spines of unequal size; the two equatorial, and their sheaths twice as large as the four polar spines. These six spines are six-edged, pyramidal, and their basal half enveloped by very large conical sheaths which are sulcate, and twice as broad on the dentate distal mouth as on the narrower base. The other fourteen spines are very thin, two-edged, half as long, with low sheaths. Approaches some forms of _Diploconus_.

_Dimensions._--Diameter of the shell 0.15; length of the equatorial spines 0.13, of the polar spines 0.08.

_Habitat._--Indian Ocean, Belligemma, Ceylon, Haeckel, surface.

Genus 378. _Hexonaspis_,[418] n. gen.

_Definition._--#Hexalaspida# with six prominent radial spines (in the hydrotomical plane) which are not surrounded by prominent sheaths; the fourteen other spines quite rudimentary, not prominent.

The genus _Hexonaspis_ and the following _Hexacolpus_ differ from the two preceding genera in the rudimentary shape of the fourteen reduced and stunted smaller spines; these are only developed inside the shell, and are not prominent outside over its surface.

Subgenus 1. _Hexonasparium_, Haeckel.

_Definition._--Six hydrotomical spines of equal size.

1. _Hexonaspis heliosestrum_, n. sp.

All six hydrotomical spines of nearly equal size, isosceles triangular, compressed, smooth, about as long as the diameter of the shell and three times as long as broad at the base. This species is very similar to _Hexalaspis heliodiscus_ (Pl. 139, fig. 2), but differs in the larger size of the six marginal spines and in the complete external absence of the fourteen smaller spines.

{879}_Dimensions._--Diameter of the shell 0.13; length of the six marginal spines 0.12, basal breadth 0.04.

_Habitat._--Tropical Atlantic, Station 348, surface.

2. _Hexonaspis hexapleura_, n. sp. (Pl. 140, fig. 15).

All six hydrotomical spines of nearly equal size, triangular, compressed, six-edged, about as long as the radius of the shell and twice as long as broad on the base. Two strong prominent ribs on each flat side of the spines. Shell very thick-walled, with a very small cavity.

_Dimensions._--Diameter of the shell 0.11; length of the six marginal spines 0.06, basal breadth 0.03.

_Habitat._--South Atlantic, Station 332, surface.

3. _Hexonaspis hexagona_, n. sp.

All six hydrotomical spines of equal size, very short, triangular, only half as long as broad at the base. The whole shell accordingly forms a regular hexagon, the six corners of which are formed by the distal points of the rudimentary spines, the six sides by their straight lateral edges. Shell very dark.

_Dimensions._--Diameter of the shell 0.2; length of the six marginal spines 0.03, basal breadth 0.06.

_Habitat._--South Atlantic (east of Patagonia), Station 318, surface.

Subgenus 2. _Hexonaspidium_, Haeckel.

_Definition._--Six hydrotomical spines of unequal size, two opposite (equatorial) much larger than the four other (polar) spines.

4. _Hexonaspis hastata_, n. sp. (Pl. 140, fig. 16).

Six hydrotomical spines of unequal size; two larger equatorial spines with six prominent wings, about as long as the radius of the shell and half as broad at the base; the four polar spines quite as broad, but only half as long, nearly equilateral triangular, with two shallow furrows on each flat side at the broader base. The fourteen smaller spines not visible on the surface, quite rudimentary. Crests of the surface elegantly denticulated.

_Dimensions._--Diameter of the shell 0.14; length of the two equatorial spines 0.08, of the four polar spines 0.04; basal breadth 0.04.

_Habitat._--Central Pacific, Station 271, surface.

{880}Genus 379. _Hexacolpus_,[419] n. gen.

_Definition._--#Hexalaspida# with six prominent radial spines (in the hydrotomical plane), which are surrounded by prominent sheaths at the base; the fourteen other spines quite rudimentary, not prominent.

The genus _Hexacolpus_ differs from the preceding _Hexonaspis_ in the development of conical or cylindrical sheaths around the basal parts of the radial spines. It bears to the latter the same relation as _Hexaconus_ exhibits to _Hexalaspis_.

Subgenus 1. _Hexacolparium_, Haeckel.

_Definition._--Six hydrotomical spines all nearly of equal size.

1. _Hexacolpus nivalis_, n. sp. (Pl. 139, fig. 1).

_Hexalaspis nivalis_, Haeckel, 1882, Manuscript et Atlas.

All six hydrotomical spines of nearly equal size and equidistant, thin, lanceolate, compressed, somewhat shorter than the diameter of the hexagonal shell. Sheaths nearly prismatic, conical in the distal third, each with twelve prominent parallel crests, which are separated by twelve deep furrows; their contracted distal opening or mouth denticulate. The sheaths are as long as the radius of the shell, and envelop two-thirds of the spines. (Resembles certain forms of snow-crystals.)

_Dimensions._--Diameter of the shell 0.15, thickness of its wall 0.08; length of the spines 0.1, of the sheath 0.007; breadth of the latter 0.04.

_Habitat._--West Tropical Pacific, Station 225, surface.

2. _Hexacolpus conifer_, n. sp.

All six hydrotomical spines of equal size and equidistant, triangular, compressed, about as long as the radius of the circular shell. Sheaths conical, sulcate, half as broad on the serrate distal end as on the base. The sheaths envelop the basal half of the spines.

_Dimensions._--Diameter of the shell 0.18; length of the spines 0.1, of the sheaths 0.06; basal breadth of the latter 0.07, distal breadth 0.04.

_Habitat._--North Pacific, Station 236, surface.

Subgenus 2. _Hexacolpidium_, Haeckel.

_Definition._--Six hydrotomical spines of unequal size, two opposite (equatorial) much larger than the four other (polar) spines.

{881}3. _Hexacolpus trypanon_, n. sp. (Pl. 140, fig. 11).

Six hydrotomical spines of unequal size, two equatorial about as long as the diameter of the shell and nearly twice as large as the four polar; all of the same form, quadrangular prismatic, with prominent edges and pointed distal ends. Sheaths six-sided prismatic, with strong prominent edges and thinner parallel ribs between them; their distal mouth with six strong denticulated teeth. The sheaths envelop two-thirds of the spines, and are as broad as the radius of the shell.

_Dimensions._--Diameter of the shell 0.13; length of the equatorial spines 0.12, of their sheaths 0.08; breadth of the latter 0.06.

_Habitat._--South Pacific, Station 288, surface.

4. _Hexacolpus dodecodus_, n. sp.

Six hydrotomical spines of unequal size, two equatorial about as long as the radius of the shell and twice as large as the four polar; all of the same form, triangular, compressed, sulcated. Sheaths prismatic, with twelve prominent, parallel edges, and twelve strong serrated triangular teeth on the mouth. The sheaths envelop the basal half of the spines. This species greatly resembles _Hexaconus serratus_ (Pl. 139, fig. 4), but differs in the larger size of the equatorial spines and the complete reduction of the fourteen smaller spines.

_Dimensions._--Diameter of the shell 0.2; length of the equatorial spines 0.1, of their sheaths 0.06; breadth of the latter 0.08.

_Habitat._--North Pacific, Station 248, surface.

5. _Hexacolpus infundibulum_, n. sp. (Pl. 140, fig. 10).

Six hydrotomical spines of unequal size, two equatorial about twice as long as the diameter of the shell and as the four polar spines; all six spines of the same form, quadrangular prismatic, pointed at the distal pyramidal end. Sheaths conical, two to three times as broad at the denticulate distal mouth as at the narrow base, sulcate; the mantle of the cone concavely vaulted. The large sheaths envelop two-thirds or three-fourths of the spines.

_Dimensions._--Diameter of the shell 0.1 to 0.13; length of the equatorial spines 0.15 to 0.2, of their sheaths 0.1 to 0.15; basal breadth of the latter 0.04, distal breadth 0.12.

_Habitat._--Central Pacific, Station 272, surface.

Family XLIV. #DIPLOCONIDA#, Haeckel (Pl. 140).

_Diploconida_, Haeckel, 1862, Monogr. d. Radiol., p.404.

_Definition._--ACANTHARIA with simple diploconical shell, composed of two very large equatorial spines which are opposite in the hydrotomical axis, are surrounded by conical or cylindrical, often compressed sheaths, and arise from a small central {882}lattice-shell. Eighteen other spines (disposed according to the Müllerian law of Icosacantha) much smaller, often rudimentary. Central capsule ellipsoidal or diploconical.

The family #Diploconida#, founded by me in 1862 for a single Mediterranean species (_Diploconus fasces_), appears to be the most aberrant and strange form among the ACANTHARIA. As I had met with only a single specimen, very dark and intransparent in its central part, my observations on its structure were imperfect and the explanation of it partly erroneous (compare my Monograph, pp. 46, 404, Taf. xx. figs. 7, 8). However, I regarded _Diploconus_ as the representative of quite a peculiar family, derived from the Acanthometrida, and I correctly compared the large opposite radial spines of one equatorial axis with the corresponding parts in _Amphilonche_.

Afterwards Richard Hertwig observed some specimens of _Diploconus fasces_ in the same locality (Messina), and gave an accurate description of its central capsule, including numerous small nuclei (1879, Organismus d. Radiol., p. 28, Taf. ii. fig. 3). He found also that the peculiar diploconical skeleton is not composed of silex, but of acanthin. In the explanation of the shell-structure he adopted my opinion.

In the rich collections of the Challenger I detected ten different forms of Diploconida, all very rare, and for the most part represented only by single specimens. A twelfth species was found by me in the collection of Captain Rabbe from the Indian Ocean. By the study of these new forms, and particularly by their comparison with the most nearly allied Hexalaspida and Belonaspida, it was possible for me to correct some errors in my former description and to give a much more correct description and natural explanation of this very peculiar and strange family of Radiolaria (compare Pl. 140).

The most characteristic and the most voluminous part of the acanthinic skeleton in all Diploconida appears as the diploconical or nearly cylindrical solid "mantle" giving them their name and odd appearance (Pl. 140). Usually this mantle is broader on its two opposite terminal openings than in its more or less constricted middle part. This latter is now more spherical or ellipsoidal, now more lenticular, and usually separated from the two cones by two slight transverse strictures. On the surface of this middle part twelve to eighteen radial spines, which in _Diplocolpus_ are rudimentary or absent, are visible in _Diploconus_. The longitudinal axis of this shell is constantly occupied by a very large pair of opposite stout prismatic or cylindrical principal spines, which are united in the centre and usually more or less prominent with their distal apex over the two openings of the double cone.

In my first communication on the _Diploconus_ (1862, _loc. cit._) I correctly compared these two large spines in the prolonged main axis of the shell to the principal equatorial spines of _Amphilonche_ (or to the "hydrotomical spines," _c_1, _c_3); but my explanation of the two peculiar cones enveloping them was erroneous. I supposed at that time that they were formed by the eight flattened and leaf-shaped curved {883}tropical spines, so that around each principal spine the four neighbouring tropical spines (two of the northern and two of the southern hemisphere) had grow together by their edges and formed the peculiar conical sheath. I can now say that this opinion (afterwards adopted also by Hertwig) was quite erroneous, the two conical or funnel-shaped sheaths being the enlarged basal sheaths of the two hydrotomical spines, which we have already seen in the Hexalaspida (Pl. 139). But whilst in these latter all six principal spines of the hydrotomical meridian plane are hypertrophied (two equatorial and four polar spines), in the nearly allied Diploconida only the two opposite equatorial spines are developed, whilst all other eighteen spines are more or less atrophied or quite rudimentary. In _Diploconus_ the latter are more or less evident, whilst in _Diplocolpus_ they disappear externally.

The true lattice-shell of the #Acanthophracta# (constantly composed of the meeting apophyses of twenty radial spines) is therefore represented in the Diploconida by the small roundish middle part of the whole shell, which is usually much smaller than the two opposite cones, and separated from them by the two slight transverse strictures. Usually this small but most important middle part of the shell is very dark and opaque, on account of its very thick wall and small pores; but in some species it is clear enough to ascertain that the structure of this lattice-shell is the same as in the lenticular Hexalaspida, there being a network of thick crests on the outer surface and small pores in the dimples between them. Indeed, in many (and probably in all) Diploconida the forty aspinal pores are present which we found in all Hexalaspida, Belonaspida, and Diporaspida, so that these four families of #Acanthophracta# represent one continuous phylogenetical series; _Phractaspis_ among the Diporaspida is at the beginning, and _Diplocolpus_ among the Diploconida at the end of this remarkably transformed morphological series.

The twenty radial spines in all Diploconida are probably united very firmly (or even perfectly grown together) in the centre of the small thick-walled lattice-shell, the inner space of which is extremely reduced. Probably, too, the sutures between the meeting apophyses of the thick radial spines are often (or even constantly) obliterated by concrescence, so that the whole shell forms a single piece of acanthin. But I regret that I cannot ascertain these and other points in the structure of the shell, as the small number of specimens observed did not permit an anatomical examination to be made. I have no doubt, however, that the structure of the whole of the middle main part of the shell is quite the same as in the lenticular shell of the thick-walled Hexalaspida, and that in both families each of the twenty radial spines bears originally only two opposite apophyses.

The characteristic mantle of the double cone of the Diploconida, or the basal sheath of their two large, perfectly developed principal spines is usually much larger than the shell itself, and more or less compressed from both poles of the shortened geotomical axis. Therefore the transverse section of the two cones is usually elliptical, more {884}rarely circular. Their widest part is generally the distal opening; more rarely this is a little constricted. The thin transparent lamella of acanthin, representing the mantle of the double cone, is commonly ribbed or furrowed by longitudinal, parallel or divergent crests, and elegantly denticulated on the edge of the distal opening.

The two conical or cylindrical halves of the mantle are connected with the two enclosed principal spines not only at the base, where they arise from the small central lattice-shell, but also throughout a certain part of their length, by means of two, four, or six wings or leaves, which lie opposite and in pairs in the meridian planes of those spines. These meridian wings are more or less triangular (with broader concave outer bases), and connected by their axial edge with the spine and by their peripheral edge with the mantle. They separate two, four, or six conical spaces or pyramidal compartments in each cone. But these aspinal compartments and the separating septa are not new productions of the Diploconida, but are inherited from their ancestral family, the Hexalaspida (compare above, p. 873).

The eighteen smaller spines in _Diploconus_ are either of nearly equal size or more or less differentiated. The eight tropical spines are often much larger than the eight polar spines. The two geotomical spines, (or the two opposite equatorial spines of the shortened geotomical axis) are often quite rudimentary. In _Diplocolpus_ the external part (outside the shell) is in all eighteen smaller spines rudimentary or atrophied.

_The Central Capsule_, as shown by Hertwig, contains numerous small nuclei, and is divided into three parts by the above named two transverse strictures; the smaller central part (in the original lenticular lattice-shell) and the two opposite larger parts, filling up the greater part of the two conical or cylindrical sheaths, and more or less adopting their form. Corresponding to the shell itself the enclosed capsule is often more or less flattened, being compressed at both poles of the geotomical axis. The pseudopodia seem to proceed only from the two large polar apertures of the sheaths, and form therefore two opposite conical tufts or bunches.

_Synopsis of the Genera of Diploconida._

All twenty spines more or less developed (sometimes eight of them rudimentary), 380. _Diploconus_.

Only the two hydrotomical spines developed (all the eighteen others rudimentary), 381. _Diplocolpus_.

Genus 380. _Diploconus_,[420] Haeckel, 1862, Monogr. d. Radiol., p. 404.

_Definition._--#Diploconida# with two very large spines (opposite in the hydrotomical axis) and ten to eighteen other much smaller spines externally visible.

{885}The genus _Diploconus_ must be derived from _Hexacolpus_ (among the _Hexalaspida_) by the stronger development of the two hydrotomical spines and their large sheaths; all the other eighteen spines are much smaller, and usually devoid of prominent sheaths. Sometimes the eight tropical spines are rudimentary.

Subgenus 1. _Diploconulus_, Haeckel.

_Definition._--Mantle of the double cone not compressed; its transverse section therefore circular.

1. _Diploconus amalla_, n. sp. (Pl. 140, fig. 1).

Mantle of the double cone thick walled, not compressed, its transverse section circular; its contour little convex; its surface nearly smooth; its distal margin regularly denticulated. Diameter of its mouth twice as large as the equatorial diameter of the shell and one-third as long as its total length. The two large spines prismatic, one-fourth longer than their conical sheath. The eighteen smaller spines very thin, about half as long as the former, a little curved.

_Dimensions._--Length of the shell 0.3; equatorial breadth 0.05, polar breadth 0.1.

_Habitat._--Central Pacific, station 271, surface.

2. _Diploconus cyathiscus_, n. sp. (Pl. 140, fig. 3).

Mantle of the double cone thin walled, not compressed; its transverse section circular; its contour strongly convex; its surface with six stronger and many smaller ribs; its margin with numerous straight and long, parallel denticles. Diameter of its mouth half as long as the whole shell and one and a half times as long as its equatorial diameter. The two principal spines one-fourth longer than their conical sheath. The eighteen smaller spines about half as long, thin, straight. Both geotomical spines thick and short.

_Dimensions._--Length of the shell 0.2; equatorial breadth 0.07, polar breadth 0.1.

_Habitat._--West Tropical Pacific, Station 225, surface.

3. _Diploconus cylindrus_, n. sp.

Mantle of the double cone thick walled, dark, cylindrical, not compressed; its transverse section circular; its contours straight, parallel; its surface with strong parallel straight longitudinal ribs; its margin irregularly dentated. Diameter of its mouth one-fifth as long as the whole shell and two-thirds as long as the diameter of the equatorial intumescence. The two principal spines prismatic, nearly twice as long as their cylindrical sheath. The smaller spines about half as long, thin, conical, straight. (Resembles the medial part of _Hexacolpus trypanon_, Pl. 140, fig. 11.)

_Dimensions._--Length of the shell 0.25; equatorial breadth 0.08, polar breadth 0.05.

_Habitat._--North Pacific, Station 241, surface.

{886}Subgenus 2. _Diploconium_, Haeckel.

_Definition._--Mantle of the double cone compressed from both poles of the shortened geotomical axis; its transverse section therefore elliptical.

4. _Diploconus fasces_, Haeckel.

_Diploconus fasces_, Haeckel, 1862, Monogr. d. Radiol., p. 405, Taf. xx. figs. 7, 8.

_Diploconus fasces_, R. Hertwig, 1879, Organismus d. Radiol., p. 28, Taf. ii. fig. 3.

Mantle of the double cone compressed, with elliptical transverse section; its contour straight; its surface with numerous longitudinal furrows; its margin finely denticulated. Diameter of its mouth two-fifths as long as the whole shell and three times as broad as its equatorial diameter. The two main spines one-third longer than their conical sheath, four-edged. The eighteen smaller spines thick and short, cylindrical or a little compressed.

_Dimensions._--Length of the shell 0.18; equatorial breadth 0.025, polar breadth 0.07.

_Habitat._--Mediterranean (Messina), surface.

5. _Diploconus cotyliscus_, n. sp. (Pl. 140, fig. 4).

Mantle of the double cone compressed, thin walled, with elliptical transverse section; its contour convex; surface and margin nearly smooth. Diameter of its mouth half as long as the whole shell and twice as long as its equatorial diameter. The two main spines scarcely longer than their hemispherical sheath. The smaller spines conical, straight, nearly of the same length.

_Dimensions._--Length of the shell 0.3; equatorial breadth 0.08, polar breadth 0.15.

_Habitat._--Tropical Atlantic, Station 347, surface,

6. _Diploconus saturnus_, Haeckel.

_Diploconus saturnus_, Haeckel, 1879, Natürl. Schöpfungsgesch., Aufl. vii. p. 706, Taf. xvi. fig. 11.

Mantle of the double cone compressed, thick walled, with elliptical transverse section; its contour convex; its surface with numerous deep and irregular longitudinal furrows and marginal incisions. Diameter of its mouth one-third as long as the whole shell and twice as broad as its equatorial diameter. The two hydrotomical spines short, scarcely longer than their sheath. The eighteen other spines thin, cylindrical, nearly of the same length, curved. (Resembles a sheaf.)

_Dimensions._--Length of the shell 0.24; equatorial breadth 0.04, polar breadth 0.07.

_Habitat._--South Pacific, Station 300, surface.

7. _Diploconus hexaphyllus_, n. sp. (Pl. 140, fig. 2).

Mantle of the double cone compressed, thick walled, with elliptical transverse section; its contour straight; surface with six stronger and numerous smaller straight ribs and six marginal {887}denticulate incisions. Diameter of its mouth one-third as long as the whole shell and somewhat smaller than the equatorial diameter. Hydrotomical spines about twice as long as their sheath, pyramidal, with emarginate point and six wings. Geotomical spines short and strong, pyramidal. Sixteen other spines thin, straight, conical.

_Dimensions._--Length of the shell 0.3; equatorial breadth 0.11, polar breadth 0.1.

_Habitat._--Central Pacific, Station 266, surface.

Genus 381. _Diplocolpus_,[421] n. gen.

_Definition._--#Diploconida# with only two developed, very large spines (opposite in the hydrotomical axis); all the other eighteen spines quite rudimentary or externally atrophied.

The genus _Diplocolpus_ is the last and the most modified genus among the ACANTHARIA. The eighteen smaller spines of _Diploconus_ are here quite rudimentary or have even perfectly disappeared by atrophy, so that the shell seems to consist only of the large hydrotomical spines and their enveloping sheaths.

Subgenus 1. _Diplocolpulus_, Haeckel.

_Definition._--Mantle of the double cone not compressed; its transverse section therefore circular.

1. _Diplocolpus costatus_, n. sp. (Pl. 140, fig. 7).

Mantle of the double cone thin walled, not compressed; its transverse section circular or nearly hexagonal; its contour little convex; surface with six thick longitudinal equidistant ribs and many thinner ribs between them; margin denticulate. Transverse diameter of the shell one-third as long as the longitudinal. The two hydrotomical spines thick and short, little prominent over the polar mouth. No rudiments of other spines visible externally.

_Dimensions._--Length of the shell 0.15; equatorial and polar breadth 0.05.

_Habitat._--Indian Ocean (Madagascar), Rabbe, surface.

2. _Diplocolpus cristatus_, n. sp. (Pl. 140, fig. 6).

Mantle of the double cone thick walled, not compressed; its transverse section circular or hexagonal; its contour nearly straight; surface with six thick prominent longitudinal equidistant ribs; margin irregularly dentated. Transverse diameter of the shell half as long as the longitudinal. {888}The two hydrotomical spines very thick and short, pyramidal, little prominent. Short rudiments of the eighteen other spines present, bristle-shaped.

_Dimensions._--Length of the shell 0.1, breadth 0.05.

_Habitat._--South Atlantic, Station 335, surface.

Subgenus 2. _Diplocolpium_, Haeckel.

_Definition._--Mantle of the double cone compressed from both poles of the shortened geotomical axis; its transverse section therefore elliptical.

3. _Diplocolpus serratus_, n. sp. (Pl. 140, fig. 5).

Mantle of the double cone thick walled, compressed, with elliptical transverse section; its surface with numerous delicate ribs; contour little convex; margin regularly serrate. Hydrotomical spines short, pyramidal, with six serrate wings. Transverse diameter of the shell nearly twice as great at the polar mouth as at the equator and half as long as the whole shell.

_Dimensions._--Length of the shell 0.15; breadth on the equator 0.035, on the poles 0.07.

_Habitat._--Central Pacific, Station 274, surface.

4. _Diplocolpus dentatus_, n. sp. (Pl. 140, fig. 9).

Mantle of the double cone thin walled, compressed, with elliptical transverse section; its contour straight; surface with six deeper and numerous shallower furrows; margin denticulated, with six triangular prominent larger teeth. Hydrotomical spines very large prismatic, pyramidal at the ends. Transverse diameter of the shell a little larger at the polar mouth than at the equator and half as long as the whole shell.

_Dimensions._--Length of the shell 0.2; breadth on the equator 0.08, on the poles 0.1.

_Habitat._--North Pacific, Station 244, surface.

5. _Diplocolpus sulcatus_, n. sp. (Pl. 140, fig. 8).

Mantle of the double cone thin walled, compressed, with elliptical transverse section; its contour straight; surface with twelve to sixteen deep longitudinal furrows, which are separated by thin, undulating, double edged ribs; margin little dentated. Hydrotomical spines short, pyramidal, with six dentate wings. Transverse diameter of the shell a little larger at the polar mouth than at the equator, about one-third of the whole length of the shell.

_Dimensions._--Length of the shell 0.17; breadth on the equator 0.05, on the poles 0.06.

_Habitat._--South Pacific, Station 291, surface.

Notes.

[1] The numbers preceded by L. N. refer to the list of names of authors in the Bibliography on p. clxxvi.

[2] _Sitzungsb. med.-nat. Gesellsch. Jena_, February 16, 1883.

[3] _Loc. cit._

[4] _Abhandl. d. k. Akad. d. Wiss. Berlin_, 1858, p. 28.

[5] Monogr. d. Radiol., 1862, Taf. ii. p. 253.

[6] Histologie der Radiolarien, pp. 43-73, Taf. iii.-v.

[7] _Sitzungsb. med.-nat. Gesellsch. Jena_, February 16, 1883.

[8] _Actissa_ = Radiant, [Greek: aktis].

[9] _Thalassolampe_ = Sea-scum; [Greek: thalassa] and [Greek: lampê].

[10] _Thalassopila_ = Sea-ball; [Greek: thalassa], [Greek: pila].

[11] _Thalassicolla_ = Sea-jelly, [Greek: thalassa], [Greek: kolla].

[12] _Thalassophysa_ = Sea-bladder; [Greek: thalassa], [Greek: physa.]

[13] _Collozoum_ = Jelly-animal; [Greek: kolla], [Greek: zôon].

[14] _Thalassosphæra_ = Sea-sphere; [Greek: thalassa], [Greek: sphaira].

[15] Atlantic, vol. i. p. 233, fig. 51, 1877.

[16] _Thalassoxanthium_ = Sea-burdock; [Greek: thalassa], [Greek: xanthion.]

[17] _Physematium_ = Small vesicle; [Greek: Physêmation].

[18] _Thalassoplancta_ = Floating on the sea; [Greek: thalassoplankta].

[19] Compare _Thalassoplancta cavispicula_, Monogr. d. Radiol., 1862, p. 261, Taf. iii. figs. 10-13.

[20] _Lampoxanthium_ = Scum-burdock; [Greek: lampe], [Greek: xanthion].

[21] _Loc. cit._, Taf. xxxii., xxxiii.

[22] _Belonozoum_ = Needle-animal; [Greek: belonê], [Greek: zôon].

[23] _Sphærozoum_ = Spherical animal; [Greek: sphaira], [Greek: zôon].

[24] _Rhaphidozoum_ = Needle-animal; [Greek: rhaphis], [Greek: zôon].

[25] Ethmosphærida = Liosphærida simplicia = Monosphærida anacantha.

[26] _Cenosphæra_ = Hollow sphere; [Greek: kenos], [Greek: sphaira].

[27] _Stigmosphæra_ = Sphere with central point; [Greek: stigma], [Greek: sphaira].

[28] _Ethmosphæra_ = Sieve-sphere; [Greek: êthmos], [Greek: sphaira].

[29] _Sethosphæra_ = Sieve-sphere; [Greek: sêthos], [Greek: sphaira].

[30] _Carposphærida_ = Liosphærida duplicia = Dyosphærida anacantha.

[31] _Carposphæra_ = Fruit-shaped sphere, [Greek: karpos], [Greek: sphaira].

[32] _Liosphæra_ = Smooth sphere; [Greek: leios], [Greek: sphaira].

[33] Thecosphærida = Liosphærida triplicia = Triosphærida anacantha.

[34] _Thecosphæra_ = Capsule-sphere; [Greek: thêkê], [Greek: sphaira].

[35] _Rhodosphæra_ = Rose-sphere; [Greek: rhodon], [Greek: sphaira].

[36] Cromyosphærida = Liosphærida tetraplicia = Tetrasphærida anacantha.

[37] _Cromyosphæra_ = Onion-sphere; [Greek: chromyon], [Greek: sphaira].

[38] Caryosphærida = Liosphærida multiplicia = Polysphærida anacantha.

[39] _Caryosphæra_ = Nut-sphere; [Greek: karyon], [Greek: sphaira].

[40] Plegmosphærida = Liosphærida spongiosa = Spongosphærida anacantha.

[41] _Styptosphæra_ = Hemp-sphere; [Greek: styptos], [Greek: sphaira].

[42] _Plegmosphæra_ = Sphere of wicker-work; [Greek: plegma], [Greek: sphaira].

[43] _Spongoplegma_ = Spongy wickerwork; [Greek: spongos], [Greek: plegma].

[44] _Spongodictyon_ = Spongy network; [Greek: spongos], [Greek: diktyon].

[45] _Loc. cit._, pp. 17, 55, 1858.

[46] _Abhandl. d. k. Akad. d. Wiss. Berlin_, p. 55, 1858.

[47] _Loc. cit._, p. 530, 1862.

[48] _Loc. cit._, pp. 30, 133, 1879.

[49] _Loc. cit._, p. 471, 1881.

[50] _Loc. cit._, p. 535, Taf. xxxiv. fig. 1.

[51] _Collosphæra_ = Jelly-sphere; [Greek: kolla], [Greek: sphaira].

[52] _Tribonosphæra_ = Cloak-sphere; [Greek: tribôn], [Greek: sphaira].

[53] _Pharyngosphæra_ = Throat-sphere; [Greek: pharynx], [Greek: sphaira].

[54] _Buccinosphæra_ = Trumpet-sphere; [Greek: bykanê], [Greek: sphaira].

[55] _Acrosphæra_ = Pointed-sphere; [Greek: akros], [Greek: sphaira].

[56] _Odontosphæra_ = Teeth-sphere; [Greek: odous], [Greek: sphaira].

[57] _Choenicosphæra_ = Shell with coronel trepans; [Greek: choinikê], [Greek: sphaira].

[58] _Siphonosphæra_ = Sphere with tubes; [Greek: siphôn], [Greek: sphaira].

[59] _Mazosphæra_ = Teat-sphere; [Greek: mazos], [Greek: sphaira].

[60] _Trypanosphæra_ = Auger-sphere; [Greek: trypanon], [Greek: sphaira].

[61] _Caminosphæra_ = Chimney-sphere; [Greek: kaminos], [Greek: sphaira].

[62] _Solenosphæra_ = Sphere with tubules; [Greek: sôlên], [Greek: sphaira].

[63] _Otosphæra_ = Shell with ears; [Greek: otosphaira].

[64] _Coronosphæra_ = Coronal-sphere; [Greek: koronê], [Greek: sphaira].

[65] _Clathrosphæra_ = Lattice-sphere.

[66] _Xanthiosphæra_ = Burdock-sphere; [Greek: xanthion], [Greek: sphaira].

[67] Stylosphærida = Sphæroidea dissacantha, Prodromus, p. 449.

[68] _Xiphosphæra_ = Sword-sphere; [Greek: xiphos], [Greek: sphaira].

[69] _Xiphostylus_ = Sword style; [Greek: xiphos], [Greek: stylos].

[70] _Saturnalis_ = Similar to _Saturnus_, with a ring.

[71] _Stylosphæra_ = Sphere with styles; [Greek: stylos], [Greek: sphaira].

[72] _Sphærostylus_ = Sphere with styles; [Greek: sphaira], [Greek: stylos].

[73] _Saturnulus_ = Small _Saturnus_, with a ring.

[74] _Amphisphæra_ = Sphere with spines on both poles; [Greek: amphi], [Greek: sphaira].

[75] _Amphistylus_ = Shell with styles on both poles; [Greek: amphi], [Greek: stylos].

[76] _Saturninus_ = Similar to Saturnus, with a ring.

[77] _Stylocromyum_ = Onion with styles; [Greek: stylos], [Greek: kromyon].

[78] _Cromyostylus_ = Onion with styles; [Greek: kromyon], [Greek: stylos].

[79] _Spongolonchis_ = Spongy shell with spears; [Greek: spongos], [Greek: lonchis].

[80] _Spongostylus_ = Spongy shell with styles; [Greek: spongos], [Greek: stylos].

[81] _Spongostylidium_, diminutive of _Spongostylus_.

[82] Staurostylida = Staurosphærida simplicia = Monosphærida tetracantha.

[83] _Staurosphæra_ = Cross-sphere; [Greek: stauros], [Greek: sphaira].

[84] _Staurostylus_ = Cross-style; [Greek: stauros], [Greek: stylos].

[85] _Stylostaurus_, Style-cross; [Greek: stylos], [Greek: stauros].

[86] Staurolonchida = Staurosphærida duplicia = Dyosphærida tetracantha.

[87] _Staurolonche_ = Crossed spear; [Greek: stauros], [Greek: lonchê].

[88] _Staurancistra_ = Crossed fish-hook; [Greek: stauros], [Greek: ankistra].

[89] _Staurolonchidium_ = Diminutive from _Staurolonche_.

[90] _Stauroxiphos_ = Sword with cross; [Greek: stauros], [Greek: xiphos].

[91] Stauracontida = Staurosphærida triplicia = Triosphærida tetracantha.

[92] _Stauracontium_ = Crossed dart; [Greek: stauros], [Greek: akontion].

[93] Staurocromyida = Staurosphærida quadruplicia = Tetrasphærida tetracantha.

[94] _Staurocromyum_ = Cross-onion; [Greek: stauros], [Greek: kromyon].

[95] _Cromyostaurus_ = Onion-cross; [Greek: kromyon], [Greek: stauros].

[96] Staurocaryida = Staurosphærida multiplicia = Polysphærida tetracantha.

[97] _Staurocaryum_ = Cross-nut; [Greek: stauros], [Greek: karyon].

[98] Staurodorida = Staurosphærida spongiosa = Spongosphærida tetracantha.

[99] _Staurodoras_ = Crossed spear; [Greek: stauros], [Greek: doras].

[100] Hexastylida = Cubosphærida simplicia = Monosphærida hexacantha.

[101] _Hexastylus_ = Shell with six styles; [Greek: hexa], [Greek: stylos].

[102] _Hexastylarium_ = Shell with six styles; derivation from _Hexastylus_.

[103] _Hexastylidium_ = Shell with six styles; derivation from _Hexastylus_.

[104] Hexalonchida = Cubosphærida duplicia = Dyosphærida hexacantha.

[105] _Hexalonche_ = Shell with six spears; [Greek: hexalonchê].

[106] _Hexancistra_ = Shell with six fish-hooks; [Greek: hexankistra].

[107] _Hexaloncharium_ = Shell with six spears; derivation from _Hexalonche_.

[108] _Hexalonchidium_ = Shell with six spears; derivation from _Hexalonche_.

[109] Hexacontida = Cubosphærida triplicia = Triosphærida hexacantha.

[110] _Hexacontion_ = Shell with six darts; [Greek: hexakontion].

[111] _Hexadendron_ = Shell with six trees; [Greek: hexadendron].

[112] _Hexacontarium_ = Shell with six darts; derivation, from _Hexacontion_.

[113] Hexacromyida = Cubosphærida quadruplicia = Tetrasphærida hexacantha.

[114] _Hexacromyum_ = Onion with six rays; [Greek: hexa], [Greek: kromyon].

[115] Hexacaryida = Cubosphærida multiplicia = Polysphærida hexacantha.

[116] _Cubosphæra_ = Sphere with three axes of a cubus; [Greek: kubos], [Greek: sphaira].

[117] _Hexacaryum_ = Nut with six spines; [Greek: hexa], [Greek: karyon].

[118] Hexadorida = Cubosphærida spongiosa = Spongosphærida hexacantha.

[119] _Cubaxonium_ = Shell with three axes like those of a cube; [Greek: kubos], [Greek: axônion].

[120] _Hexadoras_ = Shell with six spears; [Greek: hexadoras].

[121] _Hexadoridium_ = Shell with six small spears; derivation from _Hexadoras_.

[122] _Acanthosphæra_ = Spiny sphere; [Greek: akantha], [Greek: sphaira].

[123] _Heliosphæra_ = Sun sphere; [Greek: hêlios], [Greek: sphaira].

[124] _Conosphæra_ = Sphere with cones; [Greek: kônos], [Greek: sphaira].

[125] _Coscinomma_ = Sieve eye; [Greek: koskinon], [Greek: omma].

[126] _Cladococcus_ = Nucleus with branches; [Greek: klados], [Greek: kokkos].

[127] _Elaphococcus_ = Shell with harts' horn-shaped spines; [Greek: elaphos], [Greek: kokkos].

[128] Haliommida = Astrosphærida duplicia = Dyosphærida polycantha.

[129] _Haliomma_ = Sea-eye; [Greek: hals], [Greek: omma].

[130] _Heliosoma_ = Sun-body; [Greek: hêlios], [Greek: sôma].

[131] _Elatomma_ = Pine-eye; [Greek: elatê], [Greek: omma].

[132] _Leptosphæra_ = Delicate sphere; [Greek: leptos], [Greek: sphaira].

[133] _Diplosphæra_ = Double sphere; [Greek: diploos], [Greek: sphaira].

[134] _Drymosphæra_ = Woody sphere; [Greek: drymos], [Greek: sphaira].

[135] _Astrosphæra_ = Star-sphere; [Greek: astron], [Greek: sphaira].

[136] Actinommida = Astrosphærida triplicia = Triosphærida polyacantha.

[137] _Actinomma_ = Radiant eye; [Greek: aktis], [Greek: omma].

[138] _Echinomma_ = Urchin-eye; [Greek: echinos], [Greek: omma].

[139] _Pityomma_ = Pine-eye; [Greek: pitys], [Greek: omma].

[140] Cromyommida = Astrosphærida quadruplicia = Tetrasphæria polyacantha.

[141] _Cromyomma_ = Onion-eye; [Greek: kromyon], [Greek: omma].

[142] _Cromyechinus_ = Onion-shaped Urchin; [Greek: kromyon], [Greek: echinos].

[143] _Cromyodrymus_ = Onion with trees; [Greek: kromyon], [Greek: drymos].

[144] Caryommida = Astrosphærida multiplica = Polysphæria polyacantha.

[145] _Caryomma_ = Nut-eye; [Greek: karyon], [Greek: omma].

[146] _Arachnopila_ = Cobweb ball; [Greek: arachnê], [Greek: pilos].

[147] _Arachnopegma_ = Cobweb-building; [Greek: arachnê], [Greek: pêgma].

[148] _Arachnosphæra_ = Cobweb-sphere; [Greek: arachnê], [Greek: sphaira].

[149] Spongiommida = Astrosphærida spongiosa = Spongosphærida polyacantha.

[150] _Spongiomma_ = Spongy-eye; [Greek: spongia], [Greek: omma].

[151] _Spongodrymus_ = Spongy wood; [Greek: spongos], [Greek: drymos].

[152] _Spongechinus_ = Spongy Urchin; [Greek: spongos], [Greek: echinos].

[153] _Spongothamnus_ = Spongy shrub; [Greek: spongos], [Greek: thamnos].

[154] _Spongopila_ = Spongy ball; [Greek: spongos], [Greek: pilos].

[155] _Rhizoplegma_ = Root-shaped wicker-work; [Greek: rhiza], [Greek: plegma].

[156] _Lychnosphæra_ = Lantern-sphere; [Greek: lychnos], [Greek: sphaira].

[157] _Centrocubus_ = Shell with a central cube; [Greek: kentron], [Greek: kubos].

[158] _Octodendron_ = Shell with eight trees; [Greek: oktô], [Greek: dendron].

[159] _Spongosphæra_ = Spongy sphere; [Greek: spongos], [Greek: sphaira].

[160] _Rhizosphæra_ = Root-sphere; [Greek: rhiza], [Greek: sphaira].

[161] _Cenellipsis_ = Hollow ellipsoid; [Greek: kenos], [Greek: elleipsis].

[162] _Axellipsis_ = Ellipsoid with an axial beam; [Greek: axis], [Greek: elleipsis].

[163] _Ellipsidium_ = Small ellipsoid; [Greek: elleipsidion].

[164] _Ellipsoxiphus_ = Ellipsoid with swords; [Greek: elleipsis], [Greek: xiphos].

[165] _Axoprunum_ = Plum with axis; [Greek: axis], [Greek: prounon].

[166] _Ellipsostylus_ = Ellipsoid with styles; [Greek: elleipsis], [Greek: stylos].

[167] _Lithomespilus_ = Siliceous medlar; [Greek: lithos], [Greek: mespilos].

[168] _Lithapium_ = Siliceous pear; [Greek: lithos], [Greek: apion].

[169] _Pipettella_ = Small pipette.

[170] _Druppula_ = Small drupe or [Greek: druppa], ripe Olive.

[171] _Druppocarpus_ = Olive-fruit; [Greek: druppa], [Greek: karpos].

[172] _Prunulum_ = Little-plum.

[173] _Prunocarpus_ = Plum fruit; [Greek: prounon], [Greek: karpos].

[174] _Cromyodruppa_ = Onion-olive; [Greek: kromyon], [Greek: druppa].

[175] _Cromyocarpus_ = Onion fruit; [Greek: kromyon], [Greek: karpos].

[176] _Lithatractus_ = Spindle of silex; [Greek: lithos], [Greek: atraktos].

[177] _Druppatractus_ = Spindle-like olive; [Greek: druppa], [Greek: atraktos].

[178] _Stylatractus_ = Spindle with styles; [Greek: stylos], [Greek: atraktos].

[179] _Xiphatractus_ = Sword-spindle; [Greek: xiphos], [Greek: atraktos].

[180] _Cromyatractus_ = Onion-spindle; [Greek: kromyon], [Greek: atraktos].

[181] _Pipetta_ = Small pipe.

[182] _Pipettaria_ = _Pipetta_-like.

[183] _Spongellipsis_ = Spongy ellipsoid; [Greek: spongos], [Greek: elleipsis].

[184] _Spongurus_ = Spongy tail; [Greek: spongos], [Greek: oura].

[185] _Spongocore_ = Spongy puppet; [Greek: spongos], [Greek: korê].

[186] _Spongoprunum_ = Spongy plum; [Greek: spongos], [Greek: prounon].

[187] _Spongodruppa_ = Spongy olive-fruit; [Greek: spongos], [Greek: druppa].

[188] _Spongatractus_ = Spongy-spindle; [Greek: spongos], [Greek: atraktos].

[189] _Spongoliva_ = Spongy olive; [Greek: spongos], [Greek: eleia].

[190] _Spongoxiphus_ = Spongy sword; [Greek: spongos], [Greek: xiphos].

[191] _Artiscus_ = Small loaf; [Greek: artiskos].

[192] _Stylartus_ = Bread with styles; [Greek: stylos], [Greek: artos].

[193] _Cannartus_ = Leaf with tubes; [Greek: kanna], [Greek: artos].

[194] _Cyphanta_ = [Greek: Kyphanta], Mediterranean port in Laconia.

[195] _Cyphonium_ = Roundish vessel; [Greek: kyphônion].

[196] _Cypassis_ = [Greek: kypassis]; A girl's girdle.

[197] _Cyphocolpus_ = Vaulted-bosom; [Greek: kyphos], [Greek: kolpos].

[198] _Cyphinus_ = [Greek: kyphinos]; derivation from [Greek: kyphos] = roundish vessel, a kind of fruit.

[199] _Cyphinidium_ = Small Cyphinus; [Greek: kyphinidion].

[200] _Cannartiscus_ = Small loaf with tubes; [Greek: kanna], [Greek: artiskos].

[201] _Cannartidium_ = Small loaf with tubules; [Greek: kanna], [Greek: artidion].

[202] _Panartus_ = quite bread-like; [Greek: panartos].

[203] _Peripanartus_ = _Panartus_ with mantle; [Greek: peripanartos].

[204] _Panicium_ = A kind of bread.

[205] _Peripanicium_ = _Panicium_ with mantle.

[206] _Panarium_ = Bread-basket.

[207] _Peripanarium_ = _Panarium_ (or bread-basket) with mantle.

[208] _Ommatocampe_ = Caterpillar with eyes; [Greek: omma], [Greek: kampê].

[209] _Ommatartus_ = Loaf with eyes; [Greek: omma], [Greek: artos].

[210] _Desmocampe_ = Chain-like caterpillar; [Greek: desmos], [Greek: kampê].

[211] _Desmartus_ = Chain-like loaf; [Greek: desmos], [Greek: artos].

[212] _Zygocampe_ = Caterpillar with paired joints; [Greek: zygon], [Greek: kampê].

[213] _Zygartus_ = Loaf with paired joints; [Greek: zygon], [Greek: artos].

[214] _Cenodiscus_ = Hollow disk; [Greek: kenos], [Greek: diskos].

[215] _Zonodiscus_ = Disk with girdle; [Greek: zônê], [Greek: diskos].

[216] _Stylodiscus_ = Disk with styles; [Greek: stylos], [Greek: diskos].

[217] _Theodiscus_ = Divine disk; [Greek: theos], [Greek: diskos].

[218] _Crucidiscus_ = Disk with cross.

[219] _Trochodiscus_ = Wheel-disk; [Greek: trochos], [Greek: diskos].

[220] _Sethodiscus_ = Sieve-disk; [Greek: sêthos], [Greek: diskos].

[221] _Phacodiscus_ = Lenticular disk; [Greek: phakos], [Greek: diskos].

[222] _Periphæna_ = Shell with transparent girdle; [Greek: periphaina].

[223] _Perizona_ = Shell with surrounding girdle; [Greek: peri], [Greek: zônê].

[224] _Sethostylus_ = Sieve with styles; [Greek: sêthos], [Greek: stylos].

[225] _Phacostylus_ = Lens with styles; [Greek: phakos], [Greek: stylos].

[226] _Triactiscus_ = Shell with three rays; [Greek: triaktiskos].

[227] _Sethostaurus_ = Sieve-cross; [Greek: sêthos], [Greek: stauros].

[228] _Phacostaurus_ = Lens with cross; [Greek: phakos], [Greek: stauros].

[229] _Distriactis_ = Shell with twice three rays; [Greek: distriaktis].

[230] _Heliosestrum_ = Sun-sieve; [Greek: hêlios], [Greek: sêstron].

[231] _Astrosestrum_ = Stellated sieve; [Greek: astron], [Greek: sêstron].

[232] _Heliodiscus_ = Sun-disk; [Greek: hêlios], [Greek: diskos].

[233] _Heliodrymus_ = Sun-forest; [Greek: hêlios], [Greek: drymos].

[234] _Astrophacus_ = Star-lens; [Greek: astron], [Greek: phakos].

[235] _Lithocyclia_ = Circular stone; [Greek: lithos], [Greek: kyklion].

[236] _Coccodiscus_ = Disk with nucleus; [Greek: kokkos], [Greek: diskos].

[237] _Stylocyclia_ = Circular shell with styles; [Greek: stylos], [Greek: kyklion].

[238] _Amphicyclia_ = Circular shell with spines on both sides; [Greek: amphi], [Greek: kyklion].

[239] _Trigonocyclia_ = Triangular shell with circular rings; [Greek: trigonon], [Greek: kyklion].

[240] _Staurocyclia_ = Circular shell with four crossed spines; [Greek: stauros], [Greek: kyklia].

[241] _Astrocyclia_ = Stellated circular shell; [Greek: astron], [Greek: kyklion].

[242] _Coccocyclia_ = Circular shell with nucleus; [Greek: kokkos], [Greek: kyklios].

[243] _Diplactura_ = Stellated shell with double tail; [Greek: diplous], [Greek: aktis], [Greek: oura].

[244] _Amphiactura_ = Stellated shell with tail on both sides; [Greek: amphi], [Greek: aktis], [Greek: oura].

[245] _Trigonactura_ = Triangular shell with three rays; [Greek: trigonon], [Greek: aktis], [Greek: oura].

[246] _Hymenactura_ = Star-shaped shell with membrane between the rays; [Greek: hymên], [Greek: aktis], [Greek: oura].

[247] _Astractura_ = Star-shaped shell with many rays; [Greek: astron], [Greek: aktis], [Greek: oura].

[248] _Stauractura_ = Cruciform shell with four rays; [Greek: stauros], [Greek: aktis], [Greek: oura].

[249] _Pentactura_ = Stellated shell with five rays; [Greek: pente], [Greek: aktis], [Greek: oura].

[250] _Echinactura_ = _Echinus_-like shell with five rays; [Greek: echinos], [Greek: aktis], [Greek: oura].

[251] _Archidiscus_ = Primordial disk; [Greek: archidiskos].

[252] _Axodiscus_ = Disk with certain axes; [Greek: axis], [Greek: diskos].

[253] _Porodiscus_ = Porous disk; [Greek: poros], [Greek: diskos].

[254] _Perichlamydium_ = Shell surrounded by a mantle; [Greek: peri], [Greek: chlamydion].

[255] _Ommatodiscus_ = Disk with eyes; [Greek: omma], [Greek: diskos].

[256] _Stomatodiscus_ = Disk with openings; [Greek: stoma], [Greek: diskos].

[257] _Xiphodictya_ = Net with swords; [Greek: xiphos], [Greek: diktyon].

[258] _Tripodictya_ = Net with tripod; [Greek: tripous], [Greek: diktyon].

[259] _Staurodictya_ = Cross-net; [Greek: stauros], [Greek: diktyon].

[260] _Stylodictya_ = Net with styles; [Greek: stylos], [Greek: diktyon].

[261] _Stylochlamydium_ = Shell with styles and mantle; [Greek: stylos], [Greek: chlamydion].

[262] _Amphibrachium_ = Shell with two arms; [Greek: amphi], [Greek: brachiôn].

[263] _Amphymenium_ = Shell with veil on both sides; [Greek: amphi], [Greek: hymênion].

[264] _Amphirrhopalum_ = Shell with clubs on both sides; [Greek: amphi], [Greek: rhopalon].

[265] _Amphicraspedum_ = Shell with borders on both sides; [Greek: amphi], [Greek: kraspedon].

[266] _Dictyastrum_ = Reticulated star; [Greek: diktyon], [Greek: astron].

[267] _Rhopalastrum_ = Club-star; [Greek: rhopalon], [Greek: astron].

[268] _Hymeniastrum_ = Membranous star; [Greek: hymên], [Greek: astron].

[269] _Euchitonia_ = Nice shell; [Greek: eu], [Greek: chitônia].

[270] _Chitonastrum_ = Star-shell; [Greek: chitônia], [Greek: astron].

[271] _Trigonastrum_ = Triangular star; [Greek: trigônon], [Greek: astron].

[272] _Stauralastrum_ = Crossed sea-star; [Greek: stauros], [Greek: hals], [Greek: astron].

[273] _Hagiastrum_ = Holy starrulet; [Greek: hagion], [Greek: astron].

[274] _Histiastrum_ = Star with enveloping tissue; [Greek: histion], [Greek: astron].

[275] _Tessarastrum_ = Starrulet with four rays; [Greek: tessara], [Greek: astron].

[276] _Stephanastrum_ = Garland-starrulet; [Greek: stephanos], [Greek: astron].

[277] _Dicranastrum_ = Fork-starrulet; [Greek: dikranon], [Greek: astron].

[278] _Myelastrum_ = Medullary starrulet; [Greek: myelos], [Greek: astron].

[279] _Pentalastrum_ = Little sea-star with five rays; [Greek: pente], [Greek: hals], [Greek: astron].

[280] _Pentinastrum_ = Starrulet with five rays; [Greek: pente], [Greek: inos], [Greek: astron].

[281] _Pentophiastrum_ = Starrulet with five snakes; [Greek: pente], [Greek: ophis], [Greek: astron].

[282] _Hexalastrum_ = Little sea-star with six rays; [Greek: hexa], [Greek: hals], [Greek: astron].

[283] _Hexinastrum_ = Starrulet with six rays; [Greek: hexa], [Greek: inos], [Greek: astron].

[284] _Triolena_ = Shell with three arms; [Greek: tria], [Greek: ôlenê].

[285] _Triopyle_ = With three gate-openings; [Greek: tria], [Greek: pylê].

[286] _Triodiscus_ = Disk with three openings; [Greek: triodiskos].

[287] _Pylolena_ = Disk with alternating gates and arms; [Greek: pylê], [Greek: ôlenê].

[288] _Hexapyle_ = With six gate-openings; [Greek: hexa], [Greek: pylê].

[289] _Pylodiscus_ = Disk with gates; [Greek: pylê], [Greek: diskos].

[290] _Discozonium_ = Disk with girdle; [Greek: diskos], [Greek: zônion].

[291] _Discopyle_ = Disk with gate; [Greek: diskos], [Greek: pylê].

[292] _Spongodiscus_ = Spongy disk; [Greek: spongos], [Greek: diskos].

[293] _Spongophacus_ = Spongy lens; [Greek: spongos], [Greek: phakos].

[294] _Spongolonche_ = Spongy disk with spontoons; [Greek: spongos], [Greek: lonchê].

[295] _Spongotripus_ = Spongy disk with tripod; [Greek: spongos], [Greek: tripous].

[296] _Spongostaurus_ = Spongy disk with crossed spines; [Greek: spongos], [Greek: stauros].

[297] _Stylotrochus_ = Wheel with styles; [Greek: stylos], [Greek: trochos].

[298] _Spongotrochus_ = Spongy wheel; [Greek: spongos], [Greek: trochos].

[299] _Spongolena_ = Spongy disk with two arms; [Greek: spongos], [Greek: ôlenê].

[300] _Spongobrachium_ = Spongy shell with two arms; [Greek: spongos], [Greek: brachiôn].

[301] _Rhopalodictyum_ = Network with clubs; [Greek: rhopalon], [Greek: diktyon].

[302] _Dictyocoryne_ = Net with clubs; [Greek: diktyon], [Greek: korynê].

[303] _Spongasteriscus_ = Spongy star; [Greek: spongos], [Greek: asteriskos].

[304] _Spongaster_ = Spongy star; [Greek: spongos], [Greek: astêr].

[305] _Cenolarcus_ = Hollow basket; [Greek: kenos], [Greek: larkos].

[306] _Larcarium_ = A kind of basket; [Greek: larkarion].

[307] _Coccolarcus_ = Basket with kernel; [Greek: kokkos], [Greek: larkos].

[308] _Larcidium_ = Little basket, diminutive of _Larcus_; [Greek: larkidion].

[309] _Spongolarcus_ = Spongy basket; [Greek: spongos], [Greek: larkos].

[310] _Stypolarcus_ = Hemp basket; [Greek: stypê], [Greek: larkos].

[311] _Larnacilla_ = Little chest, diminutive of _Larnax_; [Greek: larnax].

[312] _Larnacidium_ = Little chest, diminutive of Larnax; [Greek: larnax].

[313] _Larnacalpis_ = Tankard-shaped chest; [Greek: larnax], [Greek: kalpis].

[314] _Larnacantha_ = Chest with spines; [Greek: larnax], [Greek: akantha].

[315] _Larnacoma_ = Shell of chest form; [Greek: larnax].

[316] _Larnacospongus_ = Spongy chest; [Greek: larnax], [Greek: spongos].

[317] _Larnacostupa_ = Chest with hemp envelop; [Greek: larnax], [Greek: stupê].

[318] _Monozonium_ = With one girdle; [Greek: monozônion].

[319] _Dizonium_ = With two girdles; [Greek: dizônion].

[320] _Trizonium_ = With three girdles; [Greek: trizônion].

[321] _Amphipyle_ = With one gate on both sides; [Greek: amphi], [Greek: pylê].

[322] _Tetrapyle_ = With four gate-openings; [Greek: tetrapylê].

[323] _Octopyle_ = With eight gate-openings; [Greek: oktô], [Greek: pylê].

[324] _Pylonium_ = Building with gates; [Greek: pylônion].

[325] _Amphipylonium_ = With one large gate on either side; [Greek: amphi], [Greek: pylônion].

[326] _Tetrapylonium_ = Building with four gates; [Greek: tetra], [Greek: pylônion].

[327] _Pylozonium_ = Shell with gates and girdles; [Greek: pylê], [Greek: zônion].

[328] _Tholartus_ = Cupola-bread; [Greek: tholos], [Greek: artos].

[329] _Tholodes_ = Cupola-shaped; [Greek: tholôdês] _vel_ [Greek: tholoeidês].

[330] _Amphitholus_ = Shell with two opposite cupolas; [Greek: amphi], [Greek: tholos].

[331] _Amphitholonium_ = Small shell with two opposite cupolas; [Greek: amphi], [Greek: tholônion].

[332] _Tholostaurus_ = Cross of four cupolas; [Greek: tholos], [Greek: stauros].

[333] _Tholoma_ = Dome-building; [Greek: tholôma].

[334] Alternating, [Greek: metallassôn].

[335] _Staurotholus_ = Cupolas cross-wise disposed; [Greek: stauros], [Greek: tholos].

[336] _Staurotholonium_ = Small shell with cupolas cross-wise disposed; [Greek: stauros], [Greek: tholônion].

[337] _Tholocubus_ = Cube with six cupolas on its sides; [Greek: tholos], [Greek: kubos].

[338] _Tholonium_ = Shell with cupolas; [Greek: tholônion].

[339] _Cubotholus_ = Shell with cupolas disposed on six cube-sides; [Greek: kubos], [Greek: tholos].

[340] _Cubotholonium_ = Small shell with cupolas disposed on the six sides of a cube; [Greek: kubos], [Greek: tholônion].

[341] _Zonarium_ = Small girdle; [Greek: zônarion].

[342] _Zoniscus_ = Elegant girdle; [Greek: zôniskos].

[343] _Zonidium_ = Little girdle; [Greek: zônidion].

[344] _Spirema_ = Convolution, turning; [Greek: speirêma].

[345] _Lithelius_ = Stony sun; [Greek: lithos], [Greek: hêlios].

[346] _Larcospira_ = Spiral basket; [Greek: larkos], [Greek: speira].

[347] _Pylospira_ = Spiral shell with internal gates; [Greek: pylê], [Greek: speira].

[348] _Tholospira_ = Shell with spiral domes; [Greek: tholos], [Greek: speira].

[349] _Spironium_ = Shell with spiral structure; [Greek: speirônion].

[350] _Streblonia_ = Screw-shell; [Greek: streblônion].

[351] _Streblacantha_ = Screw-shell with spines; [Greek: streblê], [Greek: akantha].

[352] _Streblopyle_ = Screw-shell with gates; [Greek: streblê], [Greek: pylê].

[353] _Phorticium_ = Small vessel; [Greek: phortikion].

[354] _Spongophortis_ = Spongy vessel; [Greek: spongos], [Greek: phortis].

[355] _Soreuma_ = [Greek: sôreuma], heap.

[356] _Sorolarcus_ = Basket heap; [Greek: sôros], [Greek: larkos].

[357] _Actinelius_ = Radiant sun; [Greek: aktis], [Greek: hêlios].

[358] _Astrolophus_ = Star-like bunch; [Greek: astron], [Greek: lophos].

[359] _Actinastrum_ = Radiant star; [Greek: aktis], [Greek: astron].

[360] _Litholophus_ = Stony brush; [Greek: lithos], [Greek: lophos].

[361] _Chiastolus_ = With crossed arms; [Greek: chiastos], [Greek: ôlos].

[362] _Acanthochiasma_ = Spine-cross; [Greek: akantha], [Greek: chiasma].

[363] _Acanthometron_ = Spine proportion; [Greek: akantha], [Greek: metron].

[364] _Zygacantha_ = Spines opposite in pairs; [Greek: zyga], [Greek: akantha].

[365] _Acanthonia_ = Spiny article; [Greek: akantha], [Greek: ônia].

[366] _Lithophyllium_ = With stony leaves; [Greek: lithos], [Greek: phyllion].

[367] _Phractacantha_ = Spines enclosed by a hedge; [Greek: phraktos], [Greek: akantha].

[368] _Doracantha_ = Spear-like spine; [Greek: dory], [Greek: akantha].

[369] _Astrolonche_ = Star-spear; [Greek: astron], [Greek: lonchê].

[370] _Xiphacantha_ = Sword spine; [Greek: xiphos], [Greek: akantha].

[371] _Stauracantha_ = Cruciate spine; [Greek: stauros], [Greek: akantha].

[372] _Phatnacantha_ = Spine with fretwork; [Greek: phatnê], [Greek: akantha].

[373] _Pristacantha_ = Saw-spine; [Greek: pristos], [Greek: akantha].

[374] _Acanthostaurus_ = Spine-cross; [Greek: akantha], [Greek: stauros].

[375] _Belonostaurus_ = Needle cross; [Greek: belonê], [Greek: stauros].

[376] _Lonchostaurus_ = Spear-cross; [Greek: lonchê], [Greek: stauros].

[377] _Zygostaurus_ = Pair-cross; [Greek: zygon], [Greek: stauros].

[378] _Quadrilonche_ = Square-spear.

[379] _Xiphoptera_ = Sword-wing; [Greek: xiphos], [Greek: pteron].

[380] _Lithoptera_ = Stone wing; [Greek: lithos], [Greek: pteron].

[381] _Amphilonche_ = With two opposed spears; [Greek: amphi], [Greek: lonchê].

[382] _Amphibelone_ = With two opposed needles; [Greek: amphi], [Greek: belonê].

[383] _Acantholonche_ = Spiny spear; [Greek: akantha], [Greek: lonchê].

[384] _Sphærocapsa_ = Spherical capsule; [Greek: sphaira], [Greek: kapsa].

[385] _Astrocapsa_ = Star-capsule; [Greek: astron], [Greek: kapsa].

[386] _Porocapsa_ = Porous capsule; [Greek: poros], [Greek: kapsa].

[387] _Cannocapsa_ = Tubular capsule; [Greek: kanna], [Greek: kapsa].

[388] _Cenocapsa_ = Hollow Capsule; [Greek: kenos], [Greek: kapsa].

[389] _Phractaspis_ = Hedging shield; [Greek: phraktos], [Greek: aspis].

[390] _Pleuraspis_ = Shield formed by ribs; [Greek: pleura], [Greek: aspis].

[391] _Dorataspis_ = Spear on the shield; [Greek: dory], [Greek: aspis].

[392] _Diporaspis_ = Shield with two pores; [Greek: diporos], [Greek: aspis].

[393] _Orophaspis_ = Roof shield; [Greek: orophos], [Greek: aspis].

[394] _Ceriaspis_ = Dimply shield; [Greek: kêrion], [Greek: aspis].

[395] _Hystrichaspis_ = Porcupine-shield; [Greek: hystrix], [Greek: aspis].

[396] _Coscinaspis_ = Sieve-shield; [Greek: koskinon], [Greek: aspis].

[397] _Acontaspis_ = Shield with spears; [Greek: akontion], [Greek: aspis].

[398] _Stauraspis_ = Cross-shield; [Greek: stauros], [Greek: aspis].

[399] _Echinaspis_ = Urchin with shields; [Greek: echinos], [Greek: aspis].

[400] _Zonaspis_ = Shell with a girdle of shield; [Greek: zônê], [Greek: aspis].

[401] _Dodecaspis_ = Shell with twelve shields; [Greek: dôdeka], [Greek: aspis].

[402] _Tessaraspis_ = Shield with four pores; [Greek: tessara], [Greek: aspis].

[403] _Lychnaspis_ = Lantern-shield; [Greek: lychnos], [Greek: aspis].

[404] _Icosaspis_ = Shell with twenty shields; [Greek: eikosi], [Greek: aspis].

[405] _Hylaspis_ = Forest shield; [Greek: hylê], [Greek: aspis].

[406] _Phractopelta_ = Hedging shield; [Greek: phraktos], [Greek: peltê].

[407] _Pantopelta_ = Shell everywhere with shields; [Greek: pantê], [Greek: peltê].

[408] _Octopelta_ = Shell with eight shields; [Greek: oktô], [Greek: peltê].

[409] _Dorypelta_ = Spear with a light shield; [Greek: dory], [Greek: peltê].

[410] _Stauropelta_ = Cross-shield; [Greek: stauros], [Greek: peltê].

[411] _Thoracaspis_ = Cuirass-shield; [Greek: thôrax], [Greek: aspis].

[412] _Belonaspis_ = Arrow-shield; [Greek: belonê], [Greek: aspis].

[413] _Dictyaspis_ = Net-shield; [Greek: diktyon], [Greek: aspis].

[414] _Coleaspis_ = Shield with sheaths; [Greek: koleos], [Greek: aspis].

[415] _Phatnaspis_ = Panel-shield or fretwork; [Greek: phatnê], [Greek: aspis].

[416] _Hexalaspis_ = Shield with six wings; [Greek: hexalos], [Greek: aspis].

[417] _Hexaconus_ = Shell with six cones; [Greek: hexa], [Greek: kônos].

[418] _Hexonaspis_ = Shield with six auricles; [Greek: hexonos], [Greek: aspis].

[419] _Hexacolpus_ = Shell with six bosoms; [Greek: hexa], [Greek: kolpos].

[420] _Diploconus_ = Double cone; [Greek: diploos], [Greek: kônos].

[421] _Diplocolpus_ = Double bosom; [Greek: diploos], [Greek: kolpos].

* * * * *

Corrections made to printed text

Page iii, § 7: 'Radiolaria' corrected from 'Radioloria'.

Page xiv, § 29: 'Octodendron' corrected from 'Octodendrum'.

Page xvii, § 36: 'allopolar' corrected from 'alloplar'.

Page xxii, § 47: 'rhombic' corrected from 'rombic'.

Page xxvi, § 54B: 'Capsule' corrected from 'Caspule'.

Page xxxiii, § 63: 'Thalassosphærida' corrected from 'Thallassosphærida'.

Page xxxv, § 66.5: 'Nassellaria' corrected from 'Nasellaria'.

Page xlvii, § 77A: 'Mediterranean' corrected from 'Meditteranean'.

Page lxxvi, § 112: 'Phæodinida' corrected from 'Phoeodinida'; 'Cannorrhaphida' from 'Cannorhaphida'.

Page lxxxvi, § 131: Heliosphæra referred to Pl. 28, figs. 1-3 but these are not of this genus.

Page xciv, § 142B: 'Sphærozoea' corrected from 'Sphæozoea'.

Page xcix § 151: Reference to '§ 213' corrected from '§ 273'.

Page cx, § 166: 'interrupted' corrected from 'interruped'.

Page clxxiii, § 249: 'Cannorrhaphida' corrected from 'Cannorrhapida'.

Page clxxix, § 252: 'Karl' (Brandt) corrected from 'Karlt'.

Page clxxxii, § 252: 'Kenntniss' corrected from 'Kentniss'.

Page 29, Thalassosphærida, definition: 'Cannorrhaphida' corrected from 'Cannorhaphida'.

Page 36, Thalassoplancta, definition: 'Cannorrhaphis' corrected from 'Cannorhaphis'.

Page 43, Sphærozoum armatum: 'fig. 9' corrected from 'figs. 1, 9'.

Page 85, Cromyosphæra antarctica refers to Pl. 30, fig. 8 but that does not show this species

Page 87, Genus 26: 'Liosphærida' corrected from 'Liospærida'.

Page 99, Buccinosphæra invaginata, crystals: '0.008' corrected from '0.088'.

Ib., Buccinosphæra tubaria, pores: '0.008 to 0.012' corrected from '0.008 to 0.002' (cf. "three to four times as broad as the bars").

Page 130, Xiphostylus alca: 'Pl. 13' corrected from 'Pl. 14'.

Page 132, Saturnalis annularis, major axis: '0.27 to 0.3' corrected from '0.27 to 0.03'.

Page 137, Stylosphæra jugata, pores: '0.005 to 0.02' corrected from '0.005 to 0.002'.

Page 141, Sphærostylus ophidium, pores: '0.005 to 0.008' corrected from '0.05 to 0.008'.

Page 201, Hexacromyida, definition: 'concentric' corrected from 'concentic'.

Page 203, Cubosphæra concentrica, dimensions (A) and (B): '0.02' and '0.04' corrected from '0.2', '0.4' (cf. the given radial proportions).

Page 222, Coscinomma: 'n. gen.' corrected from 'n. sp.'.

Page 224, Cladococcinus: 'Subgenus' corrected from 'Sugenus'.

Page 241, Heliosoma hastatum, outer pores: '0.006' corrected from '0.06'.

Ib., Heliosoma indicum, outer pores: '0.004 to 0.01' corrected from '0.004 to 0.1' (cf. "twice to five times as broad as the bars").

Page 253, Actinomma japonicum, middle: '0.1' corrected from '0.01'.

Page 260, Pityomma piniferum, middle: '0.05' corrected from '0.5'; inner '0.025' from '0.25'.

Ib., Pityomma drymodes, middle: '0.1' corrected from '0.01'.

Page 261, Cromyomma perplexum, diameter (B): '0.13' corrected from '0.013'.

Page 271, Spongiomma spathillatum: 'Octodendron' corrected from 'Octodendrom'.

Page 291, Cenellipsis ehrenbergii, shorter axis: '0.08 to 0.1' corrected from '0.8 to 0.1'.

Page 307, synopsis, 141: 'Cromyatractus' corrected from 'Cromyotractus'.

Page 308, Druppula cocos, medullary shell: '0.03 and 0.035' corrected from '0.03 and 0.35'.

Page 309, Druppula phoenix, minor axis: '0.08' corrected from '0.8'.

Page 310, Druppula elliptica: 'irregularly' corrected from 'irreguarlly'.

Page 314, Prunulum triplex, minor axis: '0.065' corrected from '0.65'.

Page 324, Druppatractus hippocampus: 'Druppatractus' corrected from 'Druppactractus'.

Page 372, Cyphinidium apicatum, pores: '0.005 to 0.01' corrected from '0.005 to 0.001'.

Page 380, Panartus fusiformis, breadth: '0.08 to 0.1' corrected from '0.08 to 0.01'.

Ib., Panartus profundissimus, pores: '0.015' corrected from '0.15' (cf. "six to eight times as broad as the bars").

Page 405, ref. to Saturnalis: 'Pl. 13, fig. 16' corrected from 'fig. 6'.

Page 418, Trochodiscus solaris: reference to 'Heliodiscus solaster' corrected from 'solaris' per main text entry.

Page 468, Coccocyclia heliantha: 'Coccocyclia' corrected from 'Coccocylia'.

Page 469, Diplactura: reference to 'Spongolena' corrected from 'Spongolene'.

Page 485, synopsis, 236: 'Tessarastrum' corrected from 'Tesserastrum'.

Page 508, Staurodictya ocellata: 'Stylodictya' corrected from 'Stylodicta'.

Page 513, Stylodictya dujardinii: 'Stylodictya' corrected from 'Stylodicyta'.

Page 538: 'Chitonastrum dicranoides' corrected from 'Chitonastrum dicranodes' (per Index).

Page 544, Hagiastrum christi: 'Tessarastrum' corrected from 'Tesserastrum'.

Page 548, subgenus 2: 'Tessarastromma' corrected from 'Tessarostromma'.

Page 557, Pentinastrum, definition: 'Histiastrum' corrected from 'Histriastrum'.

Page 561, last paragraph: 'Archidiscus hexoniscus' corrected from 'Archidiscus hexonicus'.

Page 564, Triolena trispinosa, diameter: '0.55' corrected from '0.55'.

Page 577, Spongodiscus favus, outer meshes: '0.008 to 0.012' corrected from '0.08 to 0.012'.

Page 580, Spongolonche conostyla refers to Pl. 48, fig. 7 which does not show this species.

Page 593, Dictyocoryne trigona: (basal) 'breadth' corrected from 'breath'.

Page 606, first paragraph: 'Actilarcus' corrected from 'Actolarcus'.

Page 606, Cenolarcus: 'Actilarcus' corrected from 'Actolarcus'.

Page 608, Larcarium amphistylum, breadth: '0.12' corrected from '0.012'.

Page 612, Larcidium polyacanthum, medullary shell: '0.03 to 0.09' corrected from '0.3 to 0.09'.

Page 625, Larnacoma quadruplex, breadth (A): '0.016' corrected from '0.16'.

Ib., Larnacoma hexagonium: 'inner cortical and outer medullary' corrected from 'outer cortical and inner medullary'.

Page 632, synopsis: 'Amphipylonium' corrected from 'Amhipylonium'.

Page 654, Octopyle decastyle, breadth: '0.032' corrected from '0.32'.

Page 657, Amphipylonium spinosissimum, length of the inner cortical shell: '0.16' corrected from '0.016'.

Page 657, Amphipylonium tetraceros: 'breadth' corrected from 'breath'.

Page 660, Tholonida: (we distinguish in this) 'family' corrected from 'subfamily'.

Page 665, Tholodes, definition: 'Tholartus' corrected from 'Thalartus'.

Page 666, Amphitholus: 'lentelliptical' corrected from 'lentelleptical'. So also p. 666, Amphitholonium octostylium.

Page 677, pores: '0.004 to 0.008' corrected from '0.04 to 0.008', cf. "once to three times as broad as the bars".

Page 709, Phorticium pylonium, breadth: '0.045' corrected from '0.45'.

Page 742: 'Acanthometron elasticum' corrected from 'Acathometron'.

Page 748, Zygacantha semicompressa, habitat (author): 'Car' corrected from 'Czar'.

Page 765, Phatnacantha: 'Tessaraspida', 'Tessaraspis' corrected from 'Tesseraspida', 'Tesseraspis'.

Page 786, Amphilonche messanensis, length of the minor spines: '0.05 to 0.09' corrected from '0.5 to 0.09'.

Page 826, Coscinaspis rhacopora, diameter: '0.15' corrected from '1.15'.

Page 827, Coscinaspis orthopora: 'Phatnaspis lacunaria' corrected from 'Phatnaspis lacumaria'.

Page 834, Dodecaspis tricinata, diameter: '0.016' corrected from '0.16'.

Page 844, Icosaspis elegans, smaller pores: '0.001 to 0.003' corrected from '0.01 to 0.003'.

Page 852, Phractopelta: 'apophyses' corrected from 'aphophyses'.

Page 867, Coleaspis occulta: 'Coleaspis' corrected from 'Coleapsis'.