Chapter 9

_Monstrous Variety._--In Mr. Stutchbury’s collection, there was a specimen, with the scuta, broad, smooth, thin, and fragile, without any ridge running from the umbo to the apex, and with the occludent margin reflexed. This seemed caused by the shell having been attacked by some boring animal, and from having supported Balani. In the same specimen the first cirrus on one side was monstrously thick and curled; the second cirrus had its posterior ramus in a rudimentary condition. In Mr. Cuming’s Collection, there are small specimens with the zones of growth overlapping each other, with thick irregular margins, and with the carina distorted.

This species has cost me much trouble: I have examined vast numbers of specimens, from a tenth to half an inch in length, attached to light floating objects, such as Janthinæ and Spirulæ from the tropical oceans, which all resembled each other, and slightly differed from the common appearance of _L. anserifera_: this variety is the _Pentalasmis dilatata_ of Leach; and for a long time I considered it as a distinct species. It differs from _L. anserifera_, in the less thickness of the valves, in their being more finely and yet plainly furrowed; in the greater width of the scuta; and more especially, of that part of the valve lying between the occludent margin, and the ridge running from the umbo to the apex; in the less elongation of the area in the terga, bounded by the two occludent margins; and, lastly, in the less size of the whole individual. The trophi and cirri are absolutely identical. Lately, however, in carefully going over a great suite of specimens, all the above few distinctive characters broke down and insensibly graduated away; and I am convinced that this form is only a variety of _L. anserifera_; its different aspect being caused partly by youth, but chiefly, I suspect, from being attached to light objects floating close to the surface of the sea.

The _Lepas anserifera_ can be distinguished by the slight furrows on its valves from all the other species, excepting _L. pectinata_: this latter species can be readily known, by the close proximity in the scuta of the occludent margin, and the ridge extending from the umbo to the apex; by its carina being very narrow above the fork; by the prongs of the fork diverging at an angle of from 135° to 180°; by the thinness of its valves; by the coarseness of the furrows on them; and lastly, by there being at most in _L. pectinata_ only one filamentary appendage beneath the first cirrus.

4. LEPAS PECTINATA. Pl. I, fig. 3.

LEPAS PECTINATA. _Spengler._ Skrifter Naturhist. Selbskabet, 2, B. 2, H., 1793, Tab. X, fig. 2.

---- MURICATA (var.) _Poli._ Test. Utriusque Scicil., vol. i, Pl. vi, figs. 23, 29, 1795.

LEPAS ANSERIFERA. _Poli._ Test. Utriusque Scicil., vol. i, Pl. vi, figs. 25-27.

---- SULCATA. _Montagu._ Test. Brit., Pl. i, fig. 6, 1803.

PENTALASMIS SULCATA. _Leach._ Encyclop. Brit. Suppl., tom. iii, Pl. lvii, 1824.

---- spirulæ (!) (var.) _Leach._ Tuckey’s Congo Expedit. Appendix, 1818.

---- RADULA (var.) et SULCATUS. _Brown._ Illust. of Conchology, Pl. li, figs. 3-6, 1844.

---- INVERSUS. _Chenu._ Illust. Conchy., Pl. i, fig. 14.

ANATIFA SULCATA. _Quoy et Gaimard._ Voyage de l’Astrolabe, Pl. xciii, figs. 18, 20.[28]

[28] I may add, that I have received many specimens incorrectly labelled _A. striata_, which is properly a synonym of _L. anserifera_.

_L. valvis tenuibus, crassè sulcatis, sæpe pectinatis; scutorum cristâ prominente ab umbone ad apicem juxta marginem occludentem pertinente: furcæ carinalis cruribus inter angulos 135° et 180° divergentibus._

Valves thin, coarsely furrowed, often pectinated. Scuta with a prominent ridge extending, from the umbo to the apex, close to the occludent margin; fork of the carina with the prongs diverging at an angle of from 135° to 180°.

Filaments absent, or only one on each side.

Var. (Pl. I, fig. 3 _a_), upper part of the terga (bounded by the two occludent margins) produced and sharp; surface of all the valves often coarsely pectinated, and with the carina barbed.

Atlantic Ocean, from the North of Ireland to off Cape Horn; common, under the tropics; Mediterranean: attached to wood, cork, charcoal, sea-weed, a reed-like leaf, spirulæ, cuttle-fish bones, to a bottle together with _L. anatifera_; to a ship’s bottom, Belfast, (W. Thompson.) Often associated with _L. fascicularis_. Montagu states (‘Test. Brit.,’ p. 18) that this species is sometimes attached to the fixed _Gorgonia flabellum_.

_General Appearance._--The capitulum varies considerably in length compared to its breadth, caused chiefly by the greater or less production of the occludent portion of the terga; valves thin, brittle; the furrowed surface varies much in character, narrow and broad ridges often alternating; frequently each ridge (but more especially the ridge running from the umbo to the apex of each scutum, and sometimes that alone,) is covered with prominent, curled, flat, calcareous spines, giving the shell an appearance like that of many mollusca. Other specimens show no trace of these calcified projections. From the thinness of the valves and the depth of the furrows, the margins of the valves are sinuous. _Scuta:_ the ridge running from the umbo to the apex is unusually prominent and curved; it runs very close to the occludent margin, so that, differently from in all the other species, only a very narrow space is left between this margin and the ridge. Internal teeth, under the umbones, either sharp and prominent, or mere knobs; sometimes that on the right side is much larger than that on the left; sometimes they are nearly equal; sometimes that on the left is scarcely distinguishable. Internal basal rim absent, or barely developed.

_Terga:_ these valves have a conspicuous notch to receive the apex of the scuta; the two occludent margins either meet each other at a rectangle, or at a much smaller angle, causing the portion thus bounded to vary much in outline, area, and degree of prominence. This at first led me to think that the _P. spirulæ_ of Leach, in which the point is very sharp and prominent, was a distinct species; but there are so many intermediate forms, that the idea must be given up. I may remark, that in all the species of Lepas, the upper part of the tergum seems particularly variable. The degree of acumination of the basal portion of the tergum also varies; the internal surface sometimes has small crests radiating from the umbo.

_Carina_, broad, within deeply concave; edges sinuous, externally sometimes strongly barbed; narrow above the fork, which latter is wider than the widest upper part of the valve; prongs sharp, thin, diverging at an angle of from 135° to 180°; the rim connecting the prongs not, or only slightly, reflexed.

_Peduncle_, narrow, shorter than the capitulum.

_Filamentary Appendages_, none, or only one, short, obtuse projection on each side, on the posterior face of the swelling under the first cirrus.

_Mouth._--Mandibles, with the inferior point produced into a single pectinated tooth, rarely into two pectinated teeth; on one side of one specimen, there were only four instead of five teeth. Palpi very narrow. Maxillæ highly variable; they may be described as formed of five steps, of which the two lower ones are generally united into a single one, divided by a mere trace of a notch; or with the three lower steps blended into an irregular, projecting surface, and with even the fourth step indistinct. I have seen these two extreme forms on opposite sides of the mouth of the same individual,--on one side the maxillæ being regularly step-form, on the other the whole inferior part forming an almost straight edge, standing high up above the first notch or step which bears the two upper great spines.

_Cirri._--First pair rather far removed from the second pair, with the longer ramus about three-fourths of the length of shorter ramus of second cirrus; spine-bearing surfaces, hardly at all protuberant; lateral marginal spines on the posterior cirri rather long; caudal appendages smooth, rounded, extremely minute: penis very spinose.

_Size._--Capitulum in the largest specimen, six-tenths of an inch long; only a few arrive at this size.

_Colours_, after having been kept in spirits,--sack and cirri, especially first cirrus, clouded with pale purple; peduncle brownish; valves appear blueish in specimens not long preserved, but in specimens kept longer they become perfectly and delicately white.

_General Remarks._--Under the head of _L. anserifera_, I have made some remarks on the diagnostic characters of this species. In the thinness of the valves,--form of the carina, with the rim connecting the prongs being not, or scarcely, reflexed,--and in the shortness and narrowness of the peduncle, there is some approach to _L. australis_, and thence to _L. fascicularis_. In the form of the maxillæ,--in one specimen having the mandible on one side bearing only four teeth,--and in the frequent absence of filamentary appendages, there is some approach to the genus _Pæcilasma_; but there is no such approach in the characters derived from the capitulum. We have seen that, as in so many other species of this genus, most of the parts are variable, and this is the case to a most unusual extent in the form of the maxillæ. Dr. Leach has attached eight specific names to the specimens preserved in the British Museum.

5. LEPAS AUSTRALIS. Pl. I, fig. 5.

_L. valvis glabris, tenuibus, fragilibus; scutorum dentibus umbonalibus utrinque internis; carinæ parte superiore latâ, planâ, suprâ furcam valdè constrictâ; furcæ cruribus latis, planis, tenuibus, acuminatis, intermedio margine non relexo._

Valves smooth, thin, brittle; scuta with internal umbonal teeth on both sides. Carina with the upper part broad, flat; much constricted above the fork, which has wide, flat, thin, pointed prongs, with the intermediate rim not reflexed.

Filaments, two on each side.

Common on Laminariæ in the whole Antarctic Ocean: Bass’s Straits, Van Diemen’s Land: Bay of Islands, New Zealand, lat. 35° S.: lat. 50° S., 172° W.: coast of Patagonia, lat. 45° S.: attached to bottom of H. M. S. Beagle, lat. 50° S., Patagonia: attached to a Nullipora, (I presume a drift piece,) British Museum.

_General Appearance._--Capitulum rather obtuse and thick; valves thin, brittle, approximate, either white and transparent, or dirty-brown and opaque; or sometimes tinted internally with purple (perhaps the effects of being preserved in spirits); surface plainly marked by lines of growth, rarely marked with traces of lines radiating from the umbones. _Scuta_ with teeth on both sides, nearly equal; internal basal rim rather wide, sometimes furrowed; basal margin considerably curved inwards. _Terga_ rather wide; basal angle blunt; angle formed by the two occludent margins blunt and rounded. _Carina_ (fig. 5 _a_) with the apex blunt, flat; the middle part generally very broad; much constricted above the fork, where it is internally deeply concave, and externally carinated; fork twice as broad as the broadest upper part of the valve; with the prongs flat, broad, thin, pointed, diverging at about an angle of 75°, with the intermediate rim not at all reflexed; the fork generally not deeply imbedded in the chitine membrane of the peduncle, so as to be quite easily visible externally; sometimes there is an internal, transverse, depressed line on the fork. In young specimens, with the capitulum about a quarter of an inch long, the fork of the carina is not developed, the lower slightly inflected portion consisting simply of an oval plate, twice as wide as the upper part. Until I had carefully examined a perfect series, showing the gradual changes in this part, I did not doubt that the young specimens formed a distinct species, and named it accordingly: the shortness of the penis first made me perceive that the specimens were immature. At this early age, I may add, the filamentary appendages were not developed. _Peduncle_ either quite short, or as long as the capitulum, close under which it is considerably constricted all round.

_Filamentary Appendages._--Two on each side; one long, tapering, placed on the prosoma (in one specimen represented by a mere knob), and the second shorter, situated on the posterior margin of the swelling beneath the first cirrus.

_Mouth._--Maxillæ, with three large spines at the upper angle, and with the first step distinct, but narrow; mandibles with five teeth; in young specimens the inferior point ends in a single spine; sides of the supra-oral cavity very hairy; the membrane, forming the inner fold of the labrum, yellow and thickened in the form of a spoon.

_Cirri._--In the posterior cirri there are, at the upper lateral edges of the segments on _both_ sides, small spines; the segments in the first cirrus, and in the broad anterior ramus of the second cirrus, are hemispherically and considerably protuberant. Caudal appendages smooth.

_Size._--The largest specimen had a capitulum one inch long.

The _Colours_ (after having been long in spirit) of the valves have already been given; sack and peduncle dirty yellowish-brown, with the parts corresponding to the margins of the valves much darker brown, or almost black; segments of the cirri clouded with dark brown; body and pedicels of the cirri dirty yellowish. I have reason to believe that the colours are totally different in living specimens.

_Monstrous Varieties._--Most of the specimens from lat. 50° S., on the coast of Patagonia, were more or less deformed, with the successive zones of growth overlapping each other, and forming coarse concentric ridges. The carina in several specimens was laterally distorted.

I have already remarked that this species has some affinity to _L. pectinata_; but it is much more closely related to _L. fascicularis_, the affinity being clearly shown by the thinness and translucency of the valves, their convexity, by the width and little acumination of the upper part of the carina, by the width of the fork, and by its not being deeply imbedded. In young specimens, moreover, before the fork is fully developed, there is a remarkable similarity between the two species, in the form of this lower part of the carina. Again, the narrowness and inflection of the peduncle under the capitulum in _L. australis_, and lastly, the lateral marginal spines on both sides of the segments of the posterior cirri, all clearly indicate this same affinity to _L. fascicularis_.

I believe this species is confined to the southern ocean; and perhaps there represents _L. fascicularis_ of the northern and tropical seas. It must, judging from the number of specimens brought home by Captain Sir J. Ross, and from those previously in the British Museum, and from those collected by myself, be a very common species.

6. LEPAS FASCICULARIS. Pl. I, fig. 6.

LEPAS FASCICULARIS. _Ellis_ and _Solander_. Zoophytes, 1786, Tab. xv, fig. 5.

---- ---- _Montagu._ Test. Brit. Suppl., 1808, pp. 5, 164.

---- CYGNEA. _Spengler._ Skrifter Naturhist. Selbskabet, Bd. i, 1790, Tab. vi, fig. 8.

---- DILATA. _Donovan._ British Shells, 1804.

PENTALASMIS FASCICULARIS. _Brown._ Illust. Conch., 1844, Pl. li, fig. 2.

---- SPIRULICOLA (!) et DONOVANI (!) _Leach._ Tuckey’s Congo Expedit., p. 413, 1818.

ANATIFA VITREA. _Lamarck._ Animaux sans Vertebres.

DOSIMA FASCICULARIS. (!) _J. E. Gray._ Annals of Philosophy, vol. x, 1825.

PENTALEPAS VITREA. _Lesson._ Voyage de la Coquille. Mollusca, Pl. xvi, fig. 7, 1830.

ANATIFA OCEANICA (!) _Quoy_ et _Gaimard_. Voyage de l’Astrolabe, Pl. xciii.

_L. valvis glabris, tenuibus, pellucidis; carinâ rectangulè flexâ, parte inferiore in discum planum oblongum expansâ._

Valves smooth, thin, transparent; carina rectangularly bent, with the lower part expanded into a flat oblong disc.

Filaments, five on each side; segments of the three posterior cirri with triangular brushes of spines.

Var. (_Donovani_, of Leach.) Carina with the upper part flat, spear-shaped, externally with a narrow central ridge.

Var. (_Villosa._ Pl. I, figs. 6 _b_, _c_.) Valves placed rather distant from each other; carina extremely narrow, with the upper part of nearly the same width throughout; terga with the lower part much acuminated; body of animal finely villose.

Coasts of Great Britain and France; Baltic Sea, according to Montagu Southern United States (from Agassiz); tropical Atlantic Ocean; East-Indian Archipelago, off Borneo and Celebes; Pacific Ocean, between the Sandwich and Mariana Archipelagos; New Zealand: attached to fuci, Spirulæ Janthinæ, Velellas, often to feathers and cork; often associated with the young of _L. anserifera_, (var. _dilatata_,) and _L. pectinata_.

_General Appearance._--Capitulum highly variable in all its characters; thick and broad in proportion to its length, but the breadth is variable,--in some specimens, the capitulum being longer by one-fifth of its total length than broad; in others, one-fifth broader than long. Valves generally approximate; in some varieties, however, from the narrowness of the carina and terga, the valves stand far apart, there being an interval between the carina and scuta of nearly half the breadth of the latter. Valves excessively thin, brittle, transparent, colourless, smooth, but generally sinuous along the zones of growth, which are conspicuous: valves generally covered throughout by thin chitine membrane, which is thickly clothed, especially in the interspaces between the valves, with minute spines, barely visible to the naked eye. _Scuta_ with the lower part of the tergo-carinal margin extremely protuberant; occludent margin, more or less, but slightly reflexed, with a depressed line running from the umbo to the apex; basal margin much reflexed, but to a variable extent and at a varying angle, even up to a right angle,--an external rim or collar being thus formed. There are no distinct _internal_ teeth, but the basal margin under the umbones, is more or less distinctly produced into a rounded disc or projection, which is generally not so much outwardly reflexed as the rest of the basal margin: there is no distinct internal basal rim. The primordial valves are generally visible, but they do not lie, as in all other species, close to the basal margin, but a little above it,--the lower reflexed portion having been subsequently developed. _Terga_ flat, with the occludent margin slightly arched, and not, as in the foregoing species, formed of two sides; apex bent towards the carina; width of the lower half highly variable, owing to the varying extent to which the scutal margin is hollowed out; in some specimens, the whole lower half beneath the apex of the scuta is of nearly the same width throughout; in other specimens this lower part is spear-shaped. The widest part of the tergum either equals in width, or is only two-thirds of the width of the widest part of the carina beneath its umbo. _Carina_ (Pl. I, fig. 6 _a_) highly variable in shape, with the part above the umbo either spear-shaped and slightly concave within, or nearly flat and furnished with a central external ridge; or the upper part (fig. 6 _c_) is of equal and extreme narrowness throughout, and deeply concave within, appearing as if only the central ridge had been developed. The part below the umbo, (answering to the fork in the foregoing species,) is about one-third of the length of the whole valve, and generally twice as wide as the upper part, but in the variety with the upper part of the carina equally narrow throughout, the lower part is thrice as wide as the upper; the disc, or lower part, is generally slightly concave within, exteriorly either with or without a central ridge; basal margin rounded; lateral margin more or less curved, according to the form of the upper part. The disc is not more deeply imbedded in membrane than is the upper part of the valve. The heel or umbo is either angular and prominent, or rounded. In very young specimens the carina is simply bowed, instead of being rectangularly bent.