Part 30

_Dimensions._--The largest British specimen which I have seen was only .55 of an inch in basal diameter: specimens from Greenland and the northern United States frequently attain a diameter of three-quarters of an inch, and I have seen one single somewhat distorted specimen actually 1.6 of an inch in basal diameter. The specimens from the glacial deposits of Uddevalla and Canada appear, on an average, to attain as large or larger dimensions than those from the United States: on the other hand, the specimens from the mammaliferous and Red Crag are smaller, the largest being only .35 in basal diameter. When individuals have grown crowded together, their length is often twice, and even occasionally thrice, as great as their greatest diameter; thus I have seen a Greenland specimen 1.6 of an inch in length, and only .75 in diameter. In the British Museum there are some arctic specimens, one and a half inch in length, only half an inch in diameter at the summit (fig. 6 _c_), thence tapering downwards to a blunt point.

_Scuta_; the lines of growth are but little prominent: the surface is generally covered by disintegrating membrane. The upper ends are usually a little reflexed, so that the tips project freely as small flattened points. Internally, the articular ridge is highly prominent and somewhat reflexed: there is no adductor ridge, but a very distinct impression for the adductor muscle: the depression for the lateral depressor muscle is small, but variable. The _terga_ are rather small: the spur is short, and placed at rather less than its own width from the basi-scutal angle; the basal margin slopes a little towards the spur, of which the lower end is rounded or bluntly pointed in a variable degree. There is no longitudinal furrow, hardly even a depression. Internally, the articular ridge is very prominent in the upper part; the crests for the tergal depressores are well developed, but variable.

_Compartments._--The internal carinal margin of each compartment, from the sheath to the basis, generally, but not invariably, projects a little inwards beyond the general internal surface of the shell, in a manner not common with the other species of the genus: the basal edge of this projecting margin rests on the calcareous basis, and is crenated like the basal edges of the longitudinal parietal septa. The whole internal surface of the shell is ribbed, but the ribs are not very prominent. The parietal tubes are large, and are crossed in the upper part, and often low down, by transverse thin septa: the longitudinal parietal septa are only slightly denticulated at their bases; occasionally they divide at the basis close to the outer lamina of the parietes, making some short outer subordinate pores. In the circular furrow beneath the lower edge of the sheath, there are sometimes little ridges, dividing it into small cells: sometimes, however, this furrow is filled up by irregular knobs of calcareous matter. The _radii_ are always rather narrow, and often they form mere linear ribbons of nearly uniform width along the edges of the compartments. Their summits or edges are always more or less irregular and jagged: they form an angle with the horizon of generally above 40°. Their septa are fine, and barely or not at all denticulated. The alæ have oblique summits: their sutural edges are rather thick and distinctly crenated. _Basis_ flat, calcareous, very thin, with the surface slightly marked by radiating furrows, which furrows answer to the radiating pores that occur in the bases of most species. In a club-shaped arctic specimen, one inch and a half in length, the summit being half an inch and the base only one fifth of an inch in diameter, the basis was still calcareous, thick, and not permeated by pores.

_Mouth_: labrum with six teeth: mandibles with the fourth tooth minute or rudimentary, and the fifth generally confluent with the inferior angle. Maxillæ with generally, but not invariably, a small notch under the upper pair of great spines. _Cirri_, first pair with the rami very unequal in length, one ramus being nearly twice the length of the other; in a large specimen having a cylindrical shell the proportional numbers of the segments in the two rami of the first cirrus were ten to twenty-three; in a small conical specimen the numbers were only eight to thirteen. The second cirrus has only two or three more segments than the shorter ramus of the first pair: the third cirrus has one or two more segments than the second; but it is nevertheless decidedly longer than the second. On the dorsal surfaces of both segments of the pedicel of the third cirrus, there is a tuft of fine spines. The segments of these three pairs of cirri are not much protuberant in front. The segments of the posterior cirri have, each, four, or five, or six pairs of spines. _Penis_, with a straight, sharp, short point on the dorsal basis.

_Range, habits, &c._--I have received specimens from all parts of the coast of Great Britain and Ireland, generally attached to crustacea and mollusca, and never hitherto from rocks uncovered by the tide. This species is also attached to floating timber, sticks, fuci, and occasionally to pebbles at the bottom of the sea. Mr. Thompson has sent me specimens from twenty-five fathoms depth in Belfast Bay: others on a Pinna from _about_ fifty fathoms on the coast of Antrim; others from between three and six fathoms attached to Laminaria digitata: there is a specimen in Mr. Jeffreys' collection marked forty-five fathoms. It is often associated, both on the coasts of America and Britain, with _B. porcatus_, and though these species are so distinct, yet when both have their surfaces similarly affected by being attached, as is often the case, to large Pectens, it is not at first easy, by external characters, to distinguish them, except by close inspection of the terga, which in _B. porcatus_ are beaked and purple. The _B. crenatus_ is sometimes associated in deep water with _B. Hameri_. At Ramsgate, in Kent, I saw a rudder of a ship, in which the two or three upper feet were thickly coated with _B. balanoides_, and the two or three lower feet with _B. crenatus_ and _improvisus_ mingled, together with a few of _B. balanoides_: occasionally vessels are thickly encrusted with this species, but I have never seen an instance of its concurrence with _B. tintinnabulum_ and _amphitrite_--the commonest species on ships coming from the south. I have seen specimens from Greenland, Baffin's Bay, the coast of Labrador, and other specimens marked simply, "Arctic regions," and, again, others from the shores of Maine and Massachussetts. The arctic specimens, and those from the northern United States, are larger than the British. I have seen one single minute specimen on a crab, marked as having come from the Mediterranean. In the British Museum, amongst some specimens of _B. eburneus_, ticketed as having been sent from Jamaica, there was a small group of specimens, differing in no one essential respect from the common varieties of _B. crenatus_: at first I concluded that this was an erroneous habitat, and that the specimens had really come from the United States, where _B. eburneus_, is found as well as in the West Indies: for it appeared to me exceedingly improbable that an animal which can exist in lat. 75° N. should inhabit the hot shores of Jamaica: but subsequently I have received a specimen from Prof. Krauss, collected by himself in Algoa Bay, which is perfectly characterised, and even has the little cells in the furrow under the sheath: so that I am compelled to admit this enormous range and capability of resisting the most extreme climates. That this species should live in the tropical seas is the more surprising, as the large size of the specimens in the northern seas and in the glacial deposits, might fairly have been supposed to have indicated special adaptation for a cold climate. The great geographical range of this species accords with its range in time from the present day to the Coralline Crag period.

The specimens from the glacial deposits which I have examined, chiefly in Sir C. Lyell's collection, are very fine and large; they are often associated, like the now living individuals, with _B. porcatus_ and _Hameri_: they come from the well-known formation of Uddevalla and from Canada. There are well-characterised specimens in the mammaliferous Crag, at Bramerton and near Norwich, in Sir C. Lyell's collection, and from Sutton and other places in the Red Crag of the eastern shores of England: these specimens are decidedly not only smaller than the glacial, but than the recent English specimens; for the largest Crag specimens which I have seen had a basal diameter of only .35 of an inch. The specimens which I have seen from the Coralline Crag, and some others sent me by Krantz from the miocene formation of Flonheim bei Abzei, in Germany, had not their opercular valves, yet I cannot doubt, considering how few species there are in the present section of the genus, that I have rightly identified them.

_Diagnosis._--Under the head of _B. balanoides_ I shall make a few remarks on the diagnosis between that and the present species; as _B. improvisus_ is found on the British shores, sometimes mingled with _B. crenatus_, I may observe that, externally, the only difference consists in the edges of the radii in _B. improvisus_ being much smoother and rounded, and in the whole shell being less rugged. Internally, in _B. improvisus_ the porose basis, the presence of an adductor ridge on the under side of the scutum, the graduated teeth on each side of the central notch in the labrum, and the little inequality in length of the rami of the first pair of cirri, are clearly and amply diagnostic.

28. BALANUS GLANDULA. Pl. 7, fig. 1 _a_, 1 _b_.

_Shell white; parietes with the internal lamina generally strongly ribbed longitudinally, with the pores imperfect and small, sometimes in part absent; radii narrow, with their summits rounded. Scutum with an adductor ridge; tergum with the spur truncated and rounded._

_Habitat._--California, Mus. Cuming, Aug. Gould; attached to shells and wood, together with _B. nubilus_. Southern Pacific ocean, attached to _Pollicipes polymerus_; Mus. Brit.

_General Appearance._--Shell steeply conical, or cylindrical and elongated; dirty white; walls rugged, longitudinally folded; radii narrow, with their summits very oblique and rounded; orifice toothed. Basal diameter of largest specimen half an inch.

_Scutum_, resembling externally that of _B. crenatus_; rather broad, surface smooth; articular ridge very prominent, and articular furrow very wide; hence, when the summits of the opercular valves are worn down, the two scuta together form a square projection indenting the two terga, as in _B. balanoides_. Internally, there is a small adductor ridge, on the lower side of which there is a pit, as if for a muscle. The depression for the lateral depressor muscle is small, but variable. _Tergum_ without any longitudinal furrow, and hardly a depression: spur broad, with its lower end truncated and rounded; internally, articular ridge very prominent; crests for the depressores well developed.

_Compartments_:--The internal surface of the parietes is smooth in the upper part beneath the sheath, but generally very strongly ribbed in the lower part, the ribs being plainly denticulated at their bases; in other specimens, the ribs are very small, and even in parts quite obsolete. The parietal pores are short and imperfect, sometimes reduced to an extremely minute size, to be detected only when the walls are broken across near the basal edge, and most carefully examined; occasionally not even a trace of a pore exists. Hence in this respect, this species offers a singular case of variation. The _radii_ are narrow, and of nearly the same width from top to bottom; their very oblique summits, when well preserved, are smooth and rounded; their sutural edges are ribbed or crenated with extremely fine, smooth septa; the recipient furrow is plainly marked by these septa. The sutural edges of the alæ are crenated; their summits are less oblique than those of the radii.

_Basis_, thin, finely furrowed in lines radiating from the centre; margin sometimes deeply sinuous.

_Mouth_: labrum with the central notch rather widely open, with four teeth on each side of it: palpi with very short spines along their inner margins: mandibles with the fourth and fifth teeth forming mere knobs: maxillæ small, with a mere trace of a notch under the two great upper spines. _Cirri_; first pair with the rami unequal by three or four segments, the longer ramus being only one quarter of its own length longer than the other ramus. Second pair short, with the segments (and those of the shorter ramus of first pair) somewhat protuberant. Third pair with the rami one third longer than those of the second pair. Sixth pair with the upper segments elongated, and bearing six or seven pairs of spines.

_Affinities._--This species in general appearance closely approaches _B. crenatus_ and _balanoides_, and it is related to them in many essential parts, such as in the opercular valves. It agrees with _B. balanoides_, and differs from _B. crenatus_, in the smallness and imperfection of the parietal pores, and in the radii having rounded summits; it agrees with _B. crenatus_ in the structure of its basis, and in the prominent longitudinal ribs on the internal surface of the parietes, and differs from that species in the spur of the tergum being squarer, and in the scutum having an adductor ridge.

_Range._--From the appearance of the Californian specimens, I suspect that they had adhered to tidal shells and to wood. The specimens in the British Museum, adhering to _Pollicipes polymerus_, consist of two lots, one of unknown origin, and the other certainly brought from the southern half of the Pacific Ocean by Sir James Ross: it deserves notice, that the _Pollicipes polymerus_, the supporting object, ranges from California to the southern Pacific Ocean.

_Section_ E.

_Basis membranous._

29. BALANUS BALANOIDES. Pl. 7, fig. 2 _a_-2 _d_.

LEPAS BALANOIDES. _Linn._ Fauna Succica, 1746, et Syst. Naturæ, 1767.

---- ---- _O. Fabricius._ Fauna Groen., p. 424, 1780.

---- ---- ET CLIVATUS. _Montagu_ (!). Test. Brit., 1803.

BALANUS VULGARIS (?) _Da Costa._ Hist. Nat. Testacea, Pl. 17, fig. 7, 1778.

---- OVULARIS ET ELONGATUS. _Aug. Gould_ (!). Report, Invertebrata of Massachussetts, figs. 7 and 8, (1841).

---- PUNCTATUS, CYLINDRICUS, ELONGATUS, FISTULOSUS CLAVATUS. _Auctorum variorum_. Sed non B. punctatus, _Bruguière_, Encyclop. Method., et non B. punctatus, _Montagu_, Test. Brit.

_Parietes either solid, or cancellated, or rarely formed by a single row of pores. Tergum, with the spur bluntly or sharply pointed._

_Var._ (_a_) _with the parietes permeated by tubes; spur of tergum sharply pointed; segments in the posterior pairs of cirri, bearing from eight to ten pairs of spines_.

_Habitat._--Great Britain, France, Norway, Shetland Islands; Greenland, according to O. Fabricius; North America, in lat. 66° 34′ N.; Labrador; Nova Scotia; Massachussetts, Delaware. Extremely common, attached to rocks, shells, and wood, within the tidal limits.

I have no doubt that the present species is the _Lepas balanoides_ of Linnæus; though O. Fabricius is the only author who gives, in his "Fauna Groenlandica," a sufficient description for the species to be recognised with certainty. I believe this also is the _B. balanoides_ of Bruguière, though he is in error, as far as my experience goes, in stating that the basis is ever calcareous. I have little doubt, also, that this is the _B. vulgaris_ of Da Costa. The _B. balanoides_, in its corroded and therefore punctured state, is certainly the _B. punctatus_ of most British collections; but I do not believe it is the _B. punctatus_ of Montagu, which I have scarcely any doubt is the _Chthamalus stellatus_, so often found in the southern shores of England, and even in some of the best arranged collections, mingled with our present species.

_General Appearance._--The shell, in middle-sized and old specimens, is almost invariably folded longitudinally and irregularly; it is either dirty white or very often pale brown, and punctured from the outer lamina having been corroded, to which action it is extremely subject. In very young specimens, the surface is usually quite white and smooth. The shell is sometimes much depressed; generally conical, but when crowded together, cylindrical or club-shaped, one specimen being even more than five-and-a-half times as long as wide. In Mr. Jeffreys' collection there is a specimen 2.5 of an inch long, .45 in diameter at the summit, only .2 in the middle, and rather more than .2 near the base. Another specimen was 1.8 in length, its greatest diameter being .35 of an inch at the summit. On the other hand, I have seen a very depressed variety, with deeply folded walls, in Mr. Thompson's collection from near Dublin, which was no less than four times as wide as high; so that the difference in proportion of height and greatest width, in the two extreme specimens, was nearly as 10 to 1. Occasionally, from some unknown cause, isolated specimens become cylindrical. The orifice of the shell, in the much elongated specimens, is generally deeply toothed. The radii are always narrow, sometimes extremely narrow, and have their summits smooth and rounded.

English specimens do not usually attain half an inch in basal diameter; I have, however, seen one from near Yarmouth .9 of an inch in diameter. Specimens from Massachussetts seem rather larger than the average size of British specimens, many being .6 of an inch, and one specimen a whole inch in basal diameter.

The _opercular_ valves so closely resemble those of _B. crenatus_, that the description is necessarily comparative; in some cases they could hardly be discriminated; generally, owing to the disintegration to which this species is subject, the tips of the scuta are worn off, and hence the articular ridges together form (Pl. 7, fig. 2 _a_) a square projection, indenting the two terga; but I have examined young specimens and others when not disintegrated, in which the opercular valves, viewed externally, presented no difference whatever from those of _B. crenatus_. The _scuta_, however, are, I think, generally rather thicker, with the growth-ridges more prominent, and with the tips certainly less reflexed than is usual with _B. crenatus_. Internally, the articular ridge is rather less prominent: there is no distinct adductor ridge. The _terga_ are often rather narrower in proportion, and this especially holds good in the elongated varieties; in these latter, there is occasionally a moderately deep longitudinal furrow: the spur is often exactly the same shape as in _B. crenatus_, but it is apt to be rather longer (Pl. 7, fig. 2 _c_) and more pointed: in _var._ (_a_) it is pointed (fig. 2 _d_) in a very remarkable manner. Internally, the articular ridge is decidedly more prominent than in _B. crenatus_; the crests for the tergal depressor muscles are either well developed or almost absent. From this description it will be seen, how singularly the opercular valves of the common varieties of these two species resemble each other. I may mention that in some of the much elongated specimens, the muscles going to the opercular valves partially lose their transverse striæ, and become ligamentous.

The _Parietes_ are either quite solid, or more commonly are permeated by minute pores, or by small irregular square tubes (Pl. 7, fig. 2 _b_), which only run up each successive zone of growth, for very short distances, giving to the shell a cancellated structure, which from corrosion is often externally visible. In the rather rare variety (_a_) the parietes are permeated by regular tubes, extending up to the apices of the compartments, but crossed by transverse septa. The longitudinal septa, when such can be said to occur, in no case are denticulated at their bases. The internal surface of the parietes is either quite smooth or is traversed (Pl. 7, fig. 2 _b_) by very slight anastomosing ridges, but never, even in _var._ (_a_), by regular longitudinal ribs, as in most other species. The carinal margin of each compartment, on the inside, projects, as in _B. crenatus_, inwards, beyond the general surface of the shell, and running down, rests on the basal membrane. The lower edge of the sheath is rarely hollow beneath. The walls are lined by purplish, or pale brown, or sometimes by almost black corium; numerous tubuli penetrate the under sides of the walls and opercular valves; and it is the intersection of these tubuli that gives the punctured appearance to the often corroded surface of the shell. The _radii_ are narrow, generally very narrow; they have their upper and outer margins, as seen externally, very oblique, rounded and (when well preserved) smooth; their sutural edges are either quite smooth, or sometimes just perceptibly pitted, like the basal margin of the walls, or occasionally furnished with globular or arborescent little ridges. The _alæ_ are also very oblique, but to a variable degree, sometimes only slightly oblique: their sutural edges are either smooth or obscurely crenated. _Basis_, membranous; in some much elongated specimens, during continued growth, the basal edges of the compartments approach each other so closely as almost to touch, so that the whole shell becomes pointed at the bottom; but on careful inspection I have never failed to find, even in the most pointed specimens, a minute basal membrane; in other much elongated varieties, in which the shell has apparently become too large for the animal's body, the basal membrane, instead of being flat, becomes drawn up deeply inwards, so as to touch the surface of attachment only close round the basal edges of the shell.

_Mouth_: labrum with the teeth on each side of the central notch unusually variable in number; I have seen specimens with only two on each side, with four on each side, with five on one side and four on the other, with five on one side and none on the other, and with six on both sides; hence the total number ranges from four to twelve. Mandibles, with the fourth and fifth teeth small, or quite rudimentary. Maxillæ, with scarcely even a trace of a notch under the upper pair of spines. _Cirri_; first pair, with one ramus one third or one fourth longer than the other; in one specimen the number of segments were nine and sixteen in the two rami: second and third cirri short, very nearly equal in length, having in the just-mentioned specimen respectively ten and eleven segments; the sixth cirrus in this same specimen had twenty-five segments, each segment being about as long as broad, and supporting six pairs of spines. In the singular variety (_a_) the posterior cirri are more elongated, and each segment supports seven or eight, and in one case even ten pairs of spines! the third pair is also in this variety proportionally rather longer. At the base of the third pair there is a tuft of fine spines. The penis has not, as in _B. crenatus_, a point at its dorsal basis. The branchiæ are very little plicated.

_Varieties._