Chapter 14

The _Terga_ are developed in an extremely variable degree; they are often entirely cast off and absent. In very young specimens, they are of the same length with the carina, but after the carina has ceased to grow, the terga always increase a little, and sometimes to such a degree as to be even thirty or forty times as long as carina. When most developed (fig. 4 _a_) they are not above one third as long as the scuta, to which they lie at nearly right angles; they consist of imperfectly calcified plates, square at both ends, slightly broader and thinner at the end towards the carina, where they are a little curled inwards, than at the opposite end; they are not quite flat in any one plane; internally they are slightly concave; finally, I may add, they nearly resemble in miniature the terga of _C. virgata_. In full grown specimens, the terga almost invariably drop out and are lost; but even in this case, a long brownish cleft in the membrane of the capitulum, marks their former position. The orifice of the capitulum is usually notched between the terga, or between the clefts left by them; on each side of the notch there is a slight prominence. In some few cases, however, there is no trace of this notch. Behind the terga or the clefts, the great ear-like appendages, as we have seen, are situated.

_Carina_, rudimentary (fig. 4) and often absent; it is pointed-elliptical, and is rarely above the 1/40th of an inch long. After arriving at this full size, calcareous matter is added to the under surface over a less and less area, so that it becomes internally pointed, and finally, in place of calcareous matter, continuous sheets of chitine are spread out beneath it; hence, during the disintegration of the outer surface, the carina comes to project more and more, and at last drops out; subsequently, even the little hole in which it was imbedded, disintegrates and disappears.

_Peduncle_, cylindrical, distinctly separated from the capitulum, and generally twice or thrice as long as it: the thickness of the outer membrane generally great, but variable: surface of attachment variable, either pointed, or widely expanded, or formed into divergent projections.

_Filamentary Appendages_, seven on each side, highly developed, long and tapering; there are two beneath the basal articulation of the first cirrus, and one on the posterior margin of the pedicel of each cirrus, excepting the sixth pair; the filaments on the pedicels are nearly twice as long as the cirri themselves.

_Mouth_,--mandibles, with the five teeth nearly equidistant, and towards their bases finely pectinated on both sides; inferior angle rudimentary, often represented by a single minute spine: in one specimen, there were only four teeth on one side. Maxillæ, with five steps, not very distinct from each other, with the first step much curved. The larger of the two upper great unequal spines is pectinated, like the teeth of the mandibles; there is a third long finer spine beneath the upper large pair.

_Cirri_ rather short, broad, with the anterior faces of the segments protuberant, especially those of the first cirrus and of the anterior ramus of the second pair: spines on the anterior cirri doubly serrated. Posterior cirri, with the intermediate spines between the pairs, long; dorsal tufts, minute. On the lower segment of the pedicels of the four posterior cirri, there are two separate tufts of bristles.

_Colours_ extremely variable; sometimes five longitudinal bands of dark purple can be distinctly seen (as in _C. virgata_) on the peduncle, these bands becoming more or less confluent on the capitulum; at other times, the capitulum is more or less spotted, or often nearly uniformly purple: the sack, cirri and trophi are, also, purple.

_Size._--The largest specimen which I have seen was, including the peduncle and ears, five inches in length, the capitulum itself being rather above one inch in length, and 7/10ths of an inch in breadth.

_General Remarks._--I have come to the same conclusion with Prof. Macgillivray, concerning the variability of this form, and I believe there is only one true species. With respect to Dr. Coates’s species, viz., _Otion depressa_ and _O. saccutifera_, though I have not seen specimens, I can hardly doubt, from the insufficient characters given, that they are mere varieties.

With respect to the ear-like appendages, we shall presently see in _C. virgata_, that at corresponding points on the capitulum (Tab. III, fig. 2 _b_), there are two slight, closed prominences. According to Professor Macgillivray, in _C. aurita_, every gradation can be followed by which the appendages, at first closed, become tubular and open. The opening would ensue, if the corium became absorbed at the bottom of the appendages whilst still imperforate, for then the inner tunic would be cast off at the next moult and would not be re-formed, whilst the outer membrane would gradually disintegrate together with the other external parts of the capitulum, and not being re-formed at this point, an aperture would at last be left. These appendages have no relation to the generative system: the ovarian tubes, which surround the sack do not extend into them; nor do the ovigerous lamellæ. I believe, that their function is respiratory: the corium lining them is traversed by river-like circulatory channels, and their much-folded, tubular and open structure must freely expose a large surface to the circumambient water. Why this species should require larger respiratory organs than any other, I know not. In this species, moreover, the filamentary appendages are developed to a greater extent than in any other cirripede; in most genera, the surface of the body and of the sack suffices for respiration.

2. CONCHODERMA VIRGATA. Pl. III, fig. 2. Pl. IX, fig. 4.

LEPAS VIRGATA. _Spengler._ Skrifter Naturhist. Selbskabet., B. i, 1790, Tab. vi, fig. 9.

---- CORIACEA. _Poli._ Test. utriusque Sicil., Pl. vi, fig. 20, 1795.

---- MEMBRANACEA. _Montagu._ Test. Brit. Supp., p. 164, 1808, et Linn. Trans., vol. xi, Tab. xii, fig. 2.

CONCHODERMA VIRGATUM. _Olfers._ Magaz. Gesells. Naturfor. Freunde, Berlin, 1814, p. 177, (3d Quartel).[38]

BRANTA VIRGATA. _Oken._ Lehrbuch der Gesell., Th. ii, p. 362, 1815.

SENOCLITA FASCIATA. _Schumacher._ Essai d’un Nouveau Syst., 1817.

CINERAS VITTATA. _Leach._ Encyclop. Brit. Supp., Tom. iii, Plate. 1824.

---- CRANCHII (!) CHELONOPHILUS (!) OLFERSII (!). _Leach._ Tuckey’s Congo Expedition, p. 412, 1818.

---- MEGALEPIS (!) MONTAGUI (!) RISSOANUS. _Leach._ Zool. Journal, vol. ii, p. 208, 1825.

---- MEMBRANACEA. _Macgillivray._ Edin. New Phil. Journal, vol. xxxix, p. 171, 1845.

---- BICOLOR. _Risso._ Hist. Nat. des Productions, &c., 1826, Tom. iv, p. 383.

---- VITTATUS. _Brown._ Illust. of Conch., 1844, Pl. li, figs. 16-18.

GYMNOLEPAS CRANCHII. _De Blainville._ Dict. des Sci. Nat. Hist., 1824.

PAMINA TRILINEATA (!) (Var. Monstr.). _J. E. Gray._ Annals of Phil., vol. x, 1825.

[38] See page 136 respecting this date.

_C. Scutis trilobatis: tergis intùs concavis, apicibus introrsùm leviter curvatis: carinâ modicâ, leviter curvatâ: pedunculo in capitulum coalescente._

Scuta three-lobed: terga concave internally, with their apices slightly curved inwards: carina moderately developed, slightly curved: peduncle blending into the capitulum.

No filament attached to the pedicel of the second cirrus.

_Var. chelonophilus_ (Pl. III, fig. 2 _c_). Terga, minute, nearly straight, solid, acuminated at both ends, placed far distant from the other valves: carina, either minute and acuminated at both ends, or moderately developed and slightly arched and blunt at both ends: lateral lobes of the scuta broad: valves imperfectly calcified.

_Hab._--Mundane: extremely common on ships’ bottoms from all parts of the world. Falkland Islands. Galapagos Islands, Pacific Ocean. Attached to sea-weed, turtle and other objects. Often associated with _Conchoderma aurita_, _Lepas anatifera_, _L. Hillii_, and _L. anserifera_.

_General Appearance._ Capitulum, flattened, gradually blending into the peduncle; summit square, rarely obtusely pointed. Membrane, thin. Valves, thin, small, sometimes imperfectly calcified, very variable in shape and in proportional length, and therefore, situated at variable distances from each other, but always remote and imbedded in membrane.

_Scuta_, trilobed, consisting of an upper and lower lobe (the latter generally the broadest), united into a straight flat disc, with a third lobe standing out from the middle of the exterior margin, generally at an angle of from 50° to 70° (rarely at right angles) to the upper part, and generally (but not always) bending a little inwards. The shape of the lateral lobe varies from rounded oblong to an equilateral triangle; as it approaches this latter form, it becomes much wider than the upper or lower lobes. In one specimen, and only on one side, the scutum (fig. 2 _d_) presented five points or projections. In some specimens, the scuta are very imperfectly calcified, and consist of several quite separate beads of calcareous matter of irregular shape, held together by tough brown membrane.

_Terga_, extremely variable in shape, placed at nearly right angles to the scuta: beyond their carinal ends (fig. 2 _b_), the capitulum presents two small prominences, which are important as indicating the position of the homologous, ear-like appendages in _C. aurita_.[39] The upper ends of the terga are imbedded in membrane, and project freely like little horns for about one third of their length: this free portion exactly answers to the projecting portion, bounded by the two occludent margins, in the terga of Lepas. The freely projecting portion is generally curled inwards, and the carinal portion more or less outwards,--the form of the letter =S= being thus approached; but the curvatures are not exactly in the same plane. The whole valve is generally of nearly equal width throughout, the carinal part being a very little (but in some specimens considerably) wider; internally, it is deeply concave; both points generally are blunt and rounded. In some rare varieties (_Cineras chelonophilus_ of Leach, fig. 2 _c_), the terga are much smaller and flat, with both points sharp, the whole upper portion being much and abruptly attenuated, and internally, without a trace of a concavity. Generally, the terga are about two thirds of the length of the scuta, rarely only half their length; generally, they are separated from the apices of the scuta by about their own length, rarely by twice their own length. Generally, the terga are shorter than the carina, but sometimes a very little longer than it: generally they are distant by one third or one fourth of their own length from the apex of the carina, rarely by their entire length.

[39] These have also been observed by Dr. Coates; see ‘Journal of Acad. Nat. Sci. Philadelphia,’ vol. vi, p. 134, 1829.

_Carina_ (fig. 2 _a_), lying nearly parallel to the scuta, concave within, very slightly bowed, of nearly the same width throughout, but with the lower third beneath the umbo, generally a trace wider than the upper part. Length, variable, generally rather longer (sometimes by even one third of its own length) than the scuta, but sometimes equalling only three fourths of the length of the scuta; generally longer than the terga. Upper and lower points rounded; in rare varieties, both ends are sharply acuminated. The carina and terga are generally most acuminated where they are smallest and least perfectly calcified; and consequently, in this same state, the valves stand furthest apart.

_Peduncle_, flattened, gradually widening as it joins the capitulum, to which it is generally about equal in length, or a little longer.

_Filamentary Appendages._--Six on each side (Pl. IX, fig. 4), of which one (_h_) is seated on the posterior margin of a swelling, beneath the basal articulation of the first cirrus, and this is the longest; the second (_g_) is short and thick, and is seated a little lower on the side of the prosoma, (near to this, there are also two little pap-like eminences;) the third (_i_) is seated on the posterior margin of the pedicel of the first cirrus, above the basal articulation; the fourth, fifth, and sixth (_j_, _k_, _l_) in similar positions on the pedicels of the third, fourth, and fifth cirri. These three latter filaments are shorter and smaller than the first three. At the base of the second cirrus, which has no proper filament, there is a swelling as if one had been united to it.

_Mouth._--_Mandibles_, with the basal edges of the five teeth pectinated by minute, short, strong spines on one side; inferior angle extremely short. In one specimen, there was a minute pectinated tooth between the first and second; in another, the second tooth was bifid on its summit; in another, the fourth was rudimentary.

_Maxillæ_, with five steps: sometimes each step commences with a spine rather larger than the others; at the upper angle, there are two large unequal spines (neither pectinated,) with a third longer and thinner, seated a little below. _Outer maxillæ_ (Pl. X, fig. 16), simple.

_Cirri_, with twice as many segments in the sixth cirrus as in first; spines on the first and second cirri doubly serrated.

_Colours_ (when alive).--Capitulum and peduncle grey, with a tinge of blue, with six black bands, tinged with purplish brown. The two bands near the carina become confluent on the peduncle, and sometimes disappear; the carina is edged, and the interspace between the two scuta, coloured with the same dark tint. The whole body and the pedicels of the cirri are dark lead-colour, with the segments of the cirri almost black: in some specimens, the colour seems laterally abraded from the cirri. Ova white, becoming in spirits pinkish, and then yellow. The dark bands on the capitulum and peduncle become in spirits purple; but are sometimes discharged; the general grey tint disappears. Professor Macgillivray states that many individuals are light-brown or yellowish-grey, with irregular brown streaks, or crowded dots: he states that in very young specimens the colours are paler, and the valves spicular.

_Size._--The largest specimen which I have seen, had a capitulum rather above one inch long and three fourths of an inch wide: growth very rapid.

_Monstrous Variety._--In the British Museum, there is a dried and somewhat injured specimen of a monstrous variety, the _Pamina trilineata_ of J. E. Gray: it differs from the common form only in having a tubular projection, just behind the notch separating the upper points of the terga; this tube springs from over the terga, and is, therefore, in a different position from the ear-like appendages in _Conchoderma aurita_. It does not open into the sack: the membrane composing it appears to have been double in the upper part, and to have been lined with corium: in short, this tube seems to have been an excrescence or tumour, of a cup or tubular form.

_General Remarks._--It will have been seen how much subject to variation the valves of this species are. When I first examined the _Cineras chelonophilus_ of Leach, from 36° N. lat., Atlantic Ocean, and found in many specimens, both old and young, that the terga were very small, flat, acuminated at both ends, with a projecting shoulder on the carinal margin, and situated at about their own length from the apex of the carina, and at twice their own length from the scuta; and when I found the carina acuminated at both ends, and the scuta very imperfectly calcified, with the lateral lobe broad, flat, and standing out at right angles; and lastly, when I found the whole capitulum bluntly pointed, instead of being square on the summit, I had not the least doubt, that it was a quite distinct species. Afterwards, I found in the _Cineras Olfersii_ of Leach, from the South Atlantic, the same form of terga; but within slightly more concave or furrowed, and not nearly so small, and therefore not placed at above half so great a distance from the other valves; and here, the carina had its usual outline, as had nearly the scutum on one side, whereas, on the other side, it presented a new and peculiar form, having five ridges or points, and was imperfectly calcified; seeing this, it was impossible to place much weight in the precise form or size (and therefore, relative separation,) of the calcified valves; and on close examination, I found every part of the mouth and cirri identical in Leach’s _Cineras chelonophilus_ and _C. Olfersii_, and in the common form. Therefore, I conclude, that _C. chelonophilus_, and still more _C. Olfersii_, are only varieties; the terga presenting the greatest, yet variable, amount of difference, namely, in their acumination and flatness. We know, also, that in the species of the closely allied genus of Lepas, the terga are very variable in shape, and this is the case, even in a still more marked degree, in _Conchoderma aurita_. Professor Macgillivray, I may add, has come to a similar conclusion regarding the extreme variability of the valves of this species.

As the varieties here mentioned are very remarkable, and may perhaps turn out to be true species, I think they are worth describing in some detail: I will only further add, that we must either make several new species, or consider, as I have done, several forms as mere varieties.

C. VIRGATA, var. CHELONOPHILUS of _Leach_. Pl. III, fig. 2 _c_.

Atlantic Ocean, 35° 15´ N., 16° 32´ W. On the Testudo caretta.

Capitulum not above half an inch long, composed of very thin membrane, with six bands (as stated by Leach) of faint colour; summit bluntly pointed; valves very small, far distant from each other; the scuta are imperfectly calcified, the central part of the umbo consisting of thick, brown chitine, with imbedded shelly beads; terga and carina perfectly calcified.

_Scuta_ trilobed, flat, within slightly concave, upper lobe rather more acuminated than the lower; lateral lobe triangular in outline, twice as wide as either the upper or lower lobes; lying in the same plane with them and standing out at almost exactly right angle.

_Terga_, flat; placed obliquely to the scuta, and barely half as long; separated from them by nearly twice their own length; upper and lower points acuminated; the umbo on the carinal margin forms a projecting shoulder; the scutal margin is straight, they are separated by nearly their own length from the apex of the carina.

_Carina_ narrow, very slightly arched, within slightly concave, both points acuminated; lower third rather wider than the upper part; in length equalling three fourths of the scuta, and longer by one third than the terga; about as wide as the latter.

_Filaments, Cirri, and Mouth_ exactly as before.

In some specimens sent to me by the Rev. R. T. Lowe from off the _Testudo caretta_, taken near Madeira, the scuta have their lateral lobes broad and nearly rectangular: the carina extends nearly to between the terga: the terga are nearly straight, somewhat pointed at both ends, distant from the scuta, almost solid within, with their upper points bowed outwards: the whole capitulum is bluntly pointed, as in the _var. chenophilus_, to which form this makes a rather near approach.

C. VIRGATA, var. OLFERSII.

CINERAS OLFERSII. _Leach._ Tuckey’s Congo Expedition.

_Hab._ South Atlantic Ocean.

_Scuta_, unlike on the opposite sides of the same individual, on one side with a single lateral lobe as usual, but this very narrow, on the other (fig. 2 _d_), with five lobes or projections.

_Terga_ slightly concave within, separated by a little more than their own length from the tips of the scuta, and by one third of their own length from the tip of the carina.

_Carina_ longer than the scuta by about one fifth or one sixth of its own length, blunt at both ends, considerably bowed.

Again, I possess a group of remarkably fine specimens given me by Mr. L. Reeve, from the southern ocean, (as I infer from a young _Lepas australis_ adhering to them,) in which all the individuals, young and old, are characterised as follows:--Scuta, with the lateral lobe generally broad, but to a very varying extent, with the upper and lower lobes extremely sharp. Terga separated from the scuta, by one and a fourth of their own length, and by their own length from the carina; somewhat acuminated at both ends, nearly straight, with a very slight shoulder near the umbo. Carina equalling the terga in length, and about three fourths of the length of the scuta; neither the upper nor lower point much acuminated. All the valves most imperfectly calcified: in one specimen, the scutum on one side was simply horny, without a particle of calcareous matter. The summit of the capitulum nearly intermediate in outline between the common square, and bluntly-pointed form of _var. chelonophilus_. I compared the cirri and trophi with those of a common variety, and could detect not the smallest difference. This variety differs from _var. Olfersii_, in the less development of its carina, and from _chelonophilus_, in the greater development of its carina, and especially of its terga. It would appear as if the great variability of the valves was connected with the absence of calcareous matter.

3. CONCHODERMA HUNTERI. Pl. III, fig. 3.

CINERAS HUNTERI. _R. Owen._ Cat. Mus. Coll. of Surgeons, (1830), Invert. Part I., p. 71.

_C. valvis angustis: scutis trilobatis, prominentiâ laterali non latiore quam inferior: tergorum parte superiore pæne rectangulè secundùm aperturæ marginem flexâ: carinâ valde arcuatâ: pedunculo brevi, in capitulum coalescente._

Valves, narrow: scuta, trilobed, with the lateral lobe not wider than the lower one: terga, with the upper part bent almost rectangularly along the margin of the orifice: carina considerably arched: peduncle short, blending into the capitulum.

No filament attached to the pedicel of the second cirrus.

_Var._--Carina absent; scuta, with the upper lobe absent; terga, with the rectangular projection little developed.

Attached to the skin of a snake, probably the Hydeus or Pelamis bicolor, and therefore from the tropical Indian or Pacific Oceans. Mus. Coll. of Surgeons.[40]

[40] I owe to the kindness of Professor Owen, an examination of these specimens, and information regarding them.

_Capitulum_, with the membrane very thin; summit obtusely pointed. Valves linear and thin.

_Scuta_, elongated, flat, with the upper projecting lobe rather more acuminated than the lower, and equalling it in length; lateral lobe not wider than the lower, and about as long as it, forming an angle of about 55° with the upper one.

_Terga_, of somewhat variable length, generally about half as long as the carina, narrow, and of nearly equal width throughout; lower point sharp; externally convex; internally solid, with a trace of a central depressed line; the upper fourth part generally a little bowed out of the plane of the lower part, and abruptly bent at rather above a right angle along the occludent margin of the orifice. These valves are situated at about half their own length from the upper points of the scuta.

_Carina_ considerably arched, extending to the lower points of the terga, or running up between them for even half their length; equally narrow throughout; scarcely broader than the terga; both points rounded; internally concave; the lower point does not extend as far down as that of the lower lobe of the scuta.

_Peduncle_, narrow, shorter than the capitulum, which, in the largest specimen was 4/10ths of an inch long. Longitudinal purple bands appear to have originally existed on the peduncle.