6. Alepas

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_ Genus--ALEPAS. Pl. III.

ALEPAS. Sander Rang. Manuel des Mollusques, 1829. ANATIFA. Quoy et Gaimard. Voyage de l'Astrolabe, 1834. TRITON. Lesson. Voyage de la Coquille, 1830. CINERAS. Lesson. Secundum Sander Rang.

Capitulum aut sine valvis, aut scutis corneis, pæne abditis. Capitulum without valves,[41] or with horny, almost hidden, scuta. [41] Any one not attending to the characters derived from the softer parts of the Balanidæ and Lepadidæ, might easily confound with Alepas the genus Siphonicella (genus nov.), which, undoubtedly, though having the external appearance of a pedunculated cirripede, belongs to the Balaninæ, and is closely related to Coronula. Filaments seated beneath the basal articulations of the first pair of cirri; mandibles, with two or three teeth; maxillæ notched, with the lower part irregular, projecting; caudal appendages multi-articulate.

Attached to various living objects, fixed or floating.

Capitulum either entirely destitute of valves, or with transparent horny scuta, not containing any calcareous matter, and almost hidden in membrane. These scuta are formed of a lower and a lateral lobe, placed at above right angles to each other; they are added to by successive layers, and closely resemble in shape the scuta of the Conchoderma aurita. The orifice in A. tubulosa projects so much as to be almost tubular. In A. parasita and A. minuta it does not project, and is either moderately large, or very small in proportion to the length of the capitulum; from contraction it is much wrinkled. The membrane forming the capitulum is smooth and very transparent; it contains very few tubuli, except under certain irregular projections in A. cornuta. The Peduncle is rather short and narrow; it blends into the capitulum, and is not, in some of the species, separated from it by any distinct line; the surface of attachment is rather wide. Within the peduncle we have the three usual layers of striæ-less muscles; namely, the innermost and longitudinal, which run lower down than the others; the middle and transverse; and, lastly, the exterior, oblique muscles, which cross each other (becoming transparent) on the rostral central line. These several muscles run up from the peduncle and surround the capitulum; from the transparency of the membranes they can be seen from the outside: they are particularly conspicuous round the orifice, which they probably serve to close. There is, in all cases, the usual adductor scutorum muscle (with transverse striæ), which is attached under the horny scuta, where such exist. The fact of the striæ-less muscles of the peduncle surrounding the whole capitulum, has been observed only in one other genus, namely Anelasma. In consequence of this structure, the capitulum must possess considerable powers of contraction. The antennæ of the larva in the Alepas cornuta and A. minuta have the sucking disc nearly circular, with the spines unusually plain on the distal as well as proximal margin. Basal segment broad, much constricted where united to the disc. The ultimate segment has on the middle of the outer margin, in A. cornuta, two minute spines, which I have not observed in any other cirripede: on the summit there are the usual spines. Size.--Three of the species are small. Filamentary Appendages.--These are rather small; there is only one on each side, situated on the posterior margin of a slight swelling, beneath the basal articulation of the first cirrus; and therefore in the position in which the filaments are most constant in Lepas, and where they likewise occur in Conchoderma. Body.--The prosoma is either pretty well developed or is small, according as the first cirrus is placed near to, or far from the second cirrus. Mouth.--Labrum moderately bullate, with the lower part more or less produced; crest with blunt, bead-like teeth, and short hairs. Palpi (Pl. X, fig. 8), acuminated and narrow to an unusual degree. Mandibles, with two or three teeth, and the inferior angle acuminated; the lateral bristles unusually strong, so as to give the main teeth the appearance of being pectinated. Maxillæ, widely notched, with three great upper spines; the part beneath the notch projecting, and either straight or irregular. Outer Maxillæ, with the inner bristles either continuous or divided into two groups: exteriorly there is a smaller or larger prominence, with long bristles. The olfactory orifices are either slightly, or not at all protuberant. Cirri.--In the three posterior pair, the segments have their bristles arranged in a transverse row, either in the form of a narrow brush, or consisting only of a single pair with two or three minute, intermediate, and lateral marginal spines. The anterior ramus of the second cirrus is thicker, and more thickly clothed with spines than is the posterior ramus: this latter ramus, however, and both rami of the third cirrus, are rather more thickly clothed with spines than are the three posterior pair. The unique case in A. cornuta of the inner rami of the fifth and sixth cirri being rudimentary (Pl. X, fig. 28) will be minutely described under that species. Caudal Appendages, thin, tapering, multi-articulate, about as long as the pedicels of the sixth cirrus. Stomach.--The oesophagus runs in a somewhat sinuous course, and enters the top of the stomach obliquely. There are no cæca. The biliary envelope presents a reticulated structure, instead of the usual longitudinal folds. Generative System.--The penis is hairy, not very long, and ringed or articulated in an unusually plain manner; the space between each ring being about one fourth of the diameter of the penis: the unarticulated basal portion or support is here remarkably long. The vesiculæ seminales are long, tortuous, and enter the prosoma. The ovarian tubes are of wide diameter: in A. cornuta they surround the whole capitulum. The ovigerous fræna are small, constricted at the base, and square on the free margin, which is studded with minute glandular beads, borne on the finest footstalks.

Range.--Southern shores of England, Mediterranean, Atlantic, West Indies, New Zealand, attached to various objects. A. parasita has been always taken on Medusæ.[42] [42] It appears that Solander (Dillwyn Des. Cat., vol. i, p. 34) observed a species of this genus adhering to a Medusa on the coast of Brazil. Mr. Cocks informs me that an Alepas, apparently A. parasita, has been cast on shore near Falmouth, attached to a Cyanæa; and that two other specimens adhered to the bottom of a vessel arriving at that port from Odessa.

Affinities.--This genus differs from all, except Anelasma, in the manner in which the striæ-less muscles of the peduncle run up and surround the capitulum, and likewise in the reticulated character of the biliary envelope of the stomach. To Conchoderma, especially to C. aurita, there is manifest affinity in the form of the horny scuta: there is also some affinity to this same genus in the presence of filamentary appendages though here little developed, and in the circular form of the disc of the larval antennæ, and, lastly, in the ovarian tubes in A. cornuta surrounding the capitulum. There is quite as close, if not closer affinity to Ibla, in the following peculiarities,--in the curved oesophagus,--in the general character of the cirri and trophi, with the olfactory orifices in one species in some degree prominent,--in the multi-articulated caudal appendages,--and in the plainly-articulated penis, with its elongated unarticulated support, though both these characters are exaggerated in Ibla. Lastly, the scuta in Ibla, though not at all resembling in shape those of A. cornuta, are formed without calcareous matter; and again, in Ibla, the muscles of the peduncle run up to the bases of the valves, and so almost surround the space in which the animal's body is lodged. The four species of Alepas appear to form two little groups; viz. A. parasita and A. minuta on the one hand, and A. cornuta and A. tubulosa on the other. 1. ALEPAS MINUTA. Tab. III, fig. 5.

ALEPAS MINUTA. Philippi. Enumeratio Mollusc. Siciliæ, 1836, Tab. xii, fig. 23. ---- ---- A. Costa. Esercitazione Accadem., vol. ii, part I, Naples, 1840, Pl. iii, fig. 5 (secundum Guerin in Revue Zoolog., 1841, p. 250.) ---- ---- Chenu. Illust. Conch., Pl. iii, figs. 8-10.

A. aperturâ non prominente, capituli longitudinis vix tertiam partem æquante: scutis corneis, pæne absconditis: longitudine totâ ad quartam unciæ partem. Orifice not protuberant, one third of the length of the capitulum: scuta horny, almost hidden. Total length quarter of an inch. Outer maxillæ, with the spines in front continuous; posterior cirri, with several long spines arranged in a transverse row on each segment; caudal appendages longer than the pedicels of the sixth cirrus.

Sicily; attached to a Cidaris:[43] island of Capri (A. Costa). [43] I am greatly indebted to Professor J. Müller, of Berlin, for kindly lending me specimens.

Capitulum oval, blending insensibly into the peduncle; moderately flattened; composed of thin structureless membrane, with the exception of two horny, almost quite hidden scuta. Orifice situated near the summit, and in a line, which is oblique to the longitudinal axis of the peduncle; much wrinkled; barely one third of the length of the whole capitulum. The Scuta, consist of yellowish, transparent, horny, laminated chitine, without any calcareous matter; externally covered by the common integument of the capitulum; these valves are placed very near to each other, close under the orifice, and therefore high up on the capitulum; the membrane between them is smooth and unwrinkled; they are formed of two rather acuminated lobes, joining each other at above a right angle; one lobe (the longer one) stretching nearly transversely across the capitulum, the other running down parallel to its rostral margin: in shape and position they resemble the scuta of Conchoderma aurita; and if another lobe had been developed it would have run along the orifice, and then these valves would have resembled the scuta of Conchoderma virgata. In a specimen with a capitulum 2/10ths of an inch long, the scuta from point to point were 1/20th of an inch in length. Peduncle, much wrinkled, about one third in diameter of the capitulum, and shorter than it; at the base it is generally expanded into two or three finger-like projections. Length of the largest specimen, about one fourth of an inch. Colour, according to A. Costa in the work above cited, "rufo-flava vittatâ;" but after spirits the whole becomes uniformly yellowish. Filamentary Appendages, situated beneath the basal articulation of the first cirrus, on the posterior edge of the usual enlargement; acuminated, about two thirds of the length of the shorter ramus of the first cirrus. Prosoma well developed. Mouth.--On each side there are two slight prominences; one under the mandibles, the other transverse nearer to the adductor muscle. Labrum, placed near the adductor muscle, with the upper part not more bullate than the lower part; crest with a row of blunt teeth, and many fine bristles growing chiefly outside the teeth; there are many fine bristles on the inner or supra-oesophageal fold of the labrum. Palpi not nearly touching each other, pointing towards the adductor: much hollowed out on their inner sides, hence narrow and acuminated, with doubly serrated bristles. Mandibles, with three teeth and the inferior angle ending in a single sharp spine; whole inferior portion narrow; first tooth as far from the second, as the latter from the inferior angle; owing to the presence of short thick spines projecting from the sides of the jaw, the lower edges of the second and third teeth appear pectinated. Maxillæ, nearly two thirds of the width of the mandibles; beneath the three larger upper spines there is a considerable notch, and the whole lower part is very slightly upraised; edge irregular, with obscure traces of either two projections, or perhaps of four steps. Outer Maxillæ, with bristles in front continuous; exteriorly there is a slight prominence near each olfactory orifice, with a tuft of long bristles. Cirri not much elongated; first pair placed not quite close to the second; five posterior cirri nearly equal in length; pedicels long, with irregularly scattered spines,--those on the pedicel of the first cirrus beautifully and conspicuously feathered. The segments of the three posterior pair are not very short or broad; very slightly protuberant, each with a long transverse, crescentic, narrow brush of bristles, which stand two or three deep in the middle, but on the sides are single: dorsal tufts long, and in the upper segments the spines are thick and claw-like. This structure is common to all the cirri. First cirrus with the rami unequal in length by two segments; from the shortness of the pedicel, this cirrus is much shorter than the second, but its rami are about two thirds of the length of those of the second cirrus. Second cirrus (and in a less degree the third cirrus), with the anterior ramus a shade broader than the posterior ramus, and rather more thickly covered with spines than are the three posterior cirri. Fifteen segments in the sixth cirrus; nine in the longer ramus of the first cirrus. Caudal Appendages, rather longer than the pedicels of the sixth cirrus, composed of seven cylindrical, tapering segments, each with a circle of very fine bristles on its summit. The acoustic (?) sacks are situated some way below the basal articulations of the first cirrus. 2. ALEPAS PARASITA.

ALEPAS PARASITA. Sander Rang. Man. des Mollusq., p. 364, Pl. viii, fig. 5, 1829.[44] ANATIFA UNIVALVIS. Quoy et Gaimard. Annales des Sciences, Nat., tom. x, p. 234, 1827, Pl. vii, fig. 8. ---- PARASITA. Quoy et Gaimard. Voyage de l'Astrolabe, Pl. xciii, 1834. TRITON (ALEPAS) FASCICULATUS. Lesson. Voyage de la Coquille. Mollusc. Pl. xvi, fig. 6, tom. ii, part I, 1830, p. 442. [44] M. Sander Rang rejects the specific name "univalvis," as signifying a generic character, and he has been followed in this by MM. Quoy and Gaimard themselves. This, according to the Rules of the British Association, would hardly have been a sufficient reason, but it appears that A. parasita, like A. minuta, has a pair of horny scuta or valves; and, therefore, the name univalvis is too obviously false to be retained. With respect to the generic name Triton, I fully believe that it was applied by Linnæus to the cast-off exuviæ of sessile Cirripedes.

A. aperturâ non prominente, capituli longitudinis 2/3 æquante: scutis corneis: longitudine totâ ad 2 uncias. Orifice not protuberant, equalling two thirds of the length of the capitulum: scuta horny. Total length two inches. Animal unknown.

Parasitic on Medusæ, Mediterranean and Atlantic Oceans: south shore of England(?)[45]

I have not seen this species, and have drawn up the above specific character from the Plates and brief descriptions in the Voyages of the Coquille and Astrolabe. M. Lesson thinks that his species differs from that of MM. Quoy and Gaimard; but as the peculiar yellow colour of the capitulum, general shape, short cirri, habits and range, are all common to both, I believe that they are identical. There is, however, one singular difference, namely, that the cirri are coloured bright blue in the Plate in the Voyage of the Astrolabe, and yellowish in that in the Voyage of the Coquille: this possibly may have resulted from the drawing in the latter case having been made from a specimen long kept in spirits. M. Lesson says that there are seven pair of cirri, from which I infer that this species has a pair of long, articulated, caudal appendages: he asserts that each cirrus has ten segments; the cirri are short and little curled. M. Lesson remarks, that "deux languettes bifurques occupent le bas de l'ouverture ovale:" I can hardly doubt but that these are horny scuta of nearly the same shape as in A. minuta. The whole animal seems to be extremely transparent, and of a "jaune-citron clair." MM. Quoy and Gaimard, however, remark, that different specimens vary from white to yellow. Entire length two inches, of which the capitulum is fourteen French lines. The peduncle is narrow and short.

[45] See Foot-note, p. 159.

3. ALEPAS CORNUTA. Pl. III, fig. 6. A. aperturâ parvâ, leviter prominente: scutis nullis: capitulo plerumque tribus, parvis, compressis eminentiis secundum carinalem marginem instructo. Orifice small, slightly protuberant; capitulum without horny scuta; generally with three small flattened projections along the carinal margin. Outer maxillæ with the inner bristles divided into two groups; segments of the posterior cirri extremely numerous, each with one pair of main spines; inner rami of the fifth and sixth cirri rudimentary.

St. Vincent's, West Indies, attached to an Antipathes, collected by the Rev. L. Guilding.

Capitulum globular, slightly flattened, smooth, translucent, entirely destitute of valves; orifice slightly projecting or tubular, parallel to the longitudinal axis of the peduncle, with the edges sinuous; it appears more tubular than it really is, from the convexity of the part of the capitulum immediately beneath the orifice. Three small, flexible, horny, irregular prominences project from the carinal margin; one at the bottom of the capitulum; a second about half-way up it; and a third generally close to the orifice; but their positions vary a little, and the prominences vary still more in shape and size, being either rounded and very small, or much flattened and considerably prominent; they are imperforate; in the membrane under them a few tubuli may be seen, which are not elsewhere visible; their summits are roughened with very minute points and beads of chitine; others, still minuter, are scattered over the whole capitulum. Peduncle short, narrower than the capitulum, into which it insensibly blends; strongly wrinkled; surface of attachment wide; position with respect to the branches of the coralline, various. Size and Colour.--The largest specimen, including the peduncle, was half an inch in length, and 3/10ths of an inch across the capitulum; colour, after having been long in spirits, brownish-yellow. Filamentary Appendages, one on each side, short, tapering and pointed; seated on the posterior margin of a slight swelling beneath the basal articulation of the first cirrus; they are about equal in length to the pedicels of this cirrus. The Mouth is directed abdominally; labrum much produced downwards, so as to be far separated from the adductor muscle; moderately bullate, forming about one third of the longitudinal axis of the entire mouth; upper part forming a slightly overhanging prominence; crest with a row of blunt, bead-like teeth, and externally to them there are numerous curved short bristles. Palpi (Pl. X, fig. 8,) unusually narrow, a little hollowed out along their inner margins; pointing towards the adductor muscle; thickly covered with doubly serrated bristles. Mandibles, with either two or three teeth; inferior angle narrow and tooth-like; both sides covered with strong bristles or spines, projecting beyond the toothed edge. Maxillæ, with two large upper spines, and a third rather distant from them; beneath these, there is a wide notch or hollow; inferior part square, projecting, bearing six pair of moderately long spines, (of which the central one is the longest,) mingled with finer ones. Outer Maxillæ, with a semicircular outline; the serrated bristles in front are divided into two groups; externally there is a rounded and very considerable projection covered with long bristles. Olfactory orifices slightly prominent, approximate, seated within and just beneath the rounded projections at the base of the maxillæ. Body.--Prosoma little developed; thorax small. Cirri, extremely long, but slightly curled, capable of being protruded so as almost to touch the base of the peduncle or the surface of attachment; segments short, extraordinarily numerous. In the three posterior cirri (excepting the rudimentary rami), each segment supports two long, slightly serrated spines, with two or three minute intermediate ones, and with one or two very short, thick spines on the inner and upper lateral margins: dorsal tufts with only two or three long, fine, unequal spines. All the segments are extremely flat, broad, short, with their anterior faces not protuberant; the greater number of the segments, especially the lower ones, have very obscure articulations, to be seen only with a high power, and these can be capable of little or no movement. First Cirrus placed far from the second, with the top of its pedicel on a level with the top of the lower segment of the pedicel of the second cirrus; rami short, barely half the length of those of the second cirrus; unequal, the anterior ramus being only two thirds of the length of the posterior one; the shorter ramus contains thirteen inverted-conical segments, with one side rather protuberant; the longer ramus contains twenty-three thinner segments; the segments on both rami are clothed with bristles, arranged in two or three rows, forming narrow transverse brushes. Second Cirrus, with its pedicel long, and its rami nearly equalling in length those of the sixth pair; the two rami of nearly equal length; the anterior one rather thicker than the posterior one; this posterior ramus has fifty-five segments! The bristles on the second and third cirri are arranged on the same principle as on the three posterior pair; but from an increase in size and number of the little intermediate bristles between the main pairs, and of those on the lateral rims, the segments, especially the basal ones, of the anterior ramus of the second cirrus, are clothed with thin brushes of bristles; these same bristles, on the posterior ramus of the second, and on both rami of the third cirrus, can hardly be said to form brushes, though longer and more numerous than those on the three posterior pair of cirri. Fifth and Sixth Cirri.--These resemble each other, and have their inner or posterior rami in an almost rudimentary condition. In the sixth cirrus (Pl. X, fig. 28) the outer ramus (a) has actually sixty-three segments, whereas the rudimentary ramus (k) has only eleven, nearly cylindrical segments. These are furnished with extremely minute spines, of which those on the dorsal face are longer than those on the anterior face; the spines on the summit of the terminal segment are the longest; the segments are not half as thick as the normal ones in the outer ramus. The rudimentary ramus is only one seventh part longer than the pedicel which supports both it and the normal ramus. In the fifth cirrus, the rudimentary ramus is rather longer, and has thirteen segments, resembling those in the rudimentary ramus of the sixth. In the fourth cirrus there is no trace of this peculiar structure, the rami being equal in length and strength. The two rudimentary rami on each side are nearly straight, and seem incapable of movement; they project out behind the normal rami, and closely resemble in general appearance, the two caudal appendages; hence this cirripede, at first sight, appears to be six-tailed. Pedicels of Cirri.--The pedicel of the first pair is very short; that of the second is the longest; those of the posterior cirri decreasing in length. Upper segments short; lower segments in the second, third and fourth cirri, irregularly and rather thickly clothed with bristles, but in the fifth and sixth cirri, there is a regular double row of main spines, with some minute intermediate ones: hence there is a difference, both in the rami and in the pedicels, between the fourth cirrus and the fifth and sixth, and this is a unique case. On the dorsal surface of the pedicel of the second cirrus, there is a tuft of much feathered fine spines. Caudal Appendages.--Each consists of eight much tapering, very thin segments, furnished with a few short simple spines round their upper margins, and with a longer tuft on the terminal short segment; basal segments twice as thick as the middle ones. In length, these caudal appendages equal the pedicels of the sixth pair of cirri, and are a very little shorter than the rudimentary rami of these same cirri. General Remarks.--Having examined this species first in the genus, I fully anticipated that the very remarkable character of the inner rami of the fifth and sixth cirri being rudimentary, and serving the same function (if any) with the caudal appendages, would have been generic; but this is not the case, for Alepas cornuta cannot be separated from A. minuta without violating a clear natural affinity. 4. ALEPAS TUBULOSA.

Quoy et Gaimard. Voyage de l'Astrolabe, Pl. xciii, fig. 5, 1834.

A. aperturâ parvâ prominente et tubulosâ: scutis et prominentiis secundùm marginem carinalem, nullis. Orifice small, tubular, protuberant; capitulum without horny scuta or projections along the carinal margin. Animal unknown.

New Zealand, Tolaga Bay. Attached to a living Palinurus.

I have given the above brief character from the plate, and imperfect description in the voyage of the Astrolabe. The small and distinctly tubular orifice, and the smooth carinated edge of the globose capitulum, appear sufficiently to distinguish this species from A. cornuta. The colour is stated to have been white with violet tints. Length, two (French) lines. _

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