Class—CRUSTACEA. Sub-Class—CIRRIPEDIA. (continued 3)

Valves 5; carina with the basal end produced into a small imbedded disc; scuta convex, without internal umbonal teeth; terga almost rudimentary, scarcely broader than the carina.

Spines on the segments of the posterior cirri arranged in single transverse rows.

Madeira; attached to the Homola Cuvierii, Rev. R. T. Lowe. British Museum.[31]

General Appearance.—Capitulum highly bullate, or thick. Valves rather thick, opaque, either pale or dark flesh-red, smooth, yet rather plainly striated from the umbones. There are a few very minute spines on the membranous borders of the valves.

Scuta highly convex, broadly oval, apex broad rounded; basal margin narrow, much curved; no internal, umbonal teeth; basal internal rim strong, running up part of the occludent margin. A slightly prominent ridge, either rounded or angular, but in one specimen a narrow depressed fissure-like line, runs parallel to the occludent margin and ends near the apex in a slight notch; this fact is of interest in relation to the structure of the scuta in P. eburnea and P. fissa. The scuta are either equally or very unequally convex; in the latter case, the occludent margin of one valve is curled, so that its umbo is not quite medial.

Terga, minute, almost rudimentary, scarcely broader than the carina, and half as long as the chord of its arc; carinal margin slightly curved; scutal margin straight, with a slight prominence fitting into a notch in the scuta; basal end bluntly pointed.

Carina, (fig. 3, a) rather shorter than the scuta, extending up only to the basal ends of the terga; moderately curved; apex moderately sharp; middle part broadest, externally carinated; internally not concave, with the inner lamina of shell, at the basal end, produced into a very small oblong disc or tooth, which is only as wide as the narrowest upper part of the valve. The exterior keel does not extend on to this disc, which is slightly constricted at its origin.

Peduncle very short, narrow, ringed, and apparently without spines.

Size.—Capitulum four tenths of an inch long.

The following parts of the animal are described from some small and not well preserved specimens from Madeira, which I owe to the kindness of Mr. Lowe.

Mouth.—Labrum highly bullate in the upper part, with large, inwardly pointed, unequal teeth. Mandibles, with four large, pointed, equal-sized teeth, with the inferior angle very narrow, acuminated like a single spine. Maxillæ, with three (?) large upper spines, of which the middle one is extremely strong and long, beneath which, there is a deep notch with a single strong spine, and with the whole inferior part square and much upraised, so as to stand on a level almost with the tips of the great upper spines.

Cirri in a miserable state of preservation; first cirrus short, second cirrus with rami unequal, and I suspect the anterior one the longest; some of the other cirri also have unequal rami. The segments of the posterior cirri are not protuberant, they have on their anterior faces a single transverse row of bristles: in the upper segments, some of the spines in each dorsal tuft (which is much spread out), are much thicker, though rather shorter than those on the anterior face. This peculiar structure is common to all five posterior cirri.

Caudal Appendages.—I can only say that they are spinose on their summits.

Affinities.—This species is allied to P. eburnea in the rudimentary condition of its terga; in the disc-shaped basal end of its carina; and in the presence in some specimens, of a fissure-like line on the scuta parallel to their occludent margins. Its affinity, however, is closer to P. fissa, as is more especially shown by the remarkable arrangement of the spines on the five posterior cirri.

4. Pæcilasma fissa. Pl. II, Fig. 4.

P. valvis 7; scuto utroque è duobus juxtapositis segmentis formato; segmento altero intus dentato: tergis brevibus, ter aut quater carinâ latioribus: carinæ termino basali in discum parvum angustum infossum producto.

Valves 7; each scutum being formed of two closely approximate segments; of which one is internally toothed: terga short, three or four times as wide as the carina: carina with the basal end produced into a small, narrow, imbedded disc.

Spines on the segments of the posterior cirri arranged in single transverse rows.

Philippine Archipelago; Island of Bohol; parasitic on a spinose crab, found under a stone at low water; single specimen, in Mus., Cuming.

General Appearance.—Capitulum gibbous, broadly oval, nearly a quarter of an inch long. Valves white, smooth, moderately thick, marked by the lines of growth. The occludent segments of the scuta, and nearly the whole of the terga, and the whole of the carina, enveloped in lemon-yellow membrane, tinged with orange, but the specimen had long been kept dry.

Scuta formed of two, apparently always separate, segments, closely united, so that externally their separation is hardly visible, and does not allow of movement; the fissure thus formed runs almost in the line connecting the umbo and apex, (where in most species a ridge extends,) but a little on the carinal side of it. The occludent segment is narrowly bow-shaped, pointed at both ends, with the upper end projecting slightly beyond the apex of the lateral segment, and with the occludent margin regularly curved from end to end. The lateral segment is large, of an oval shape, with a narrow strip cut off on one side. Primordial valves very plain at the umbones of the lateral segments, but none are visible on the occludent segments; and this makes me believe that these two pieces are normally parts of a single valve; having only one specimen of P. fissa, I was not able to make out quite certainly whether the two segments are continuously united at their umbones by a non-calcified portion of valve, as is certainly the case with Dichelaspis. The basal margin of the lateral segment is narrow, inflected, and blends with the carino-tergal margin; it has an internal, prominent, basal rim, and towards the occludent margin a large, prominent, internal tooth. This internal basal rim is not parallel to the outer basal margin, but rises to a point a little way up the occludent margin, in the same manner as in P. eburnea, but in a lesser degree; in this latter species the peduncle is internally almost cut off by the large disc of its carina; here, on the other hand, it is internally almost cut off by these rims and the two large teeth of the lateral segments of the scuta.

Terga sub-triangular, short, nearly half as broad as long; three or four times as wide as the carina, and rather wider than the occludent segment of the scuta; occludent margin single, arched; carinal margin slightly arched; basal angle bluntly pointed.

Carina very narrow, much arched, running up just between the basal ends of the terga; exterior ridge enveloped in membrane; heel blunt, prominent; internally, not concave, even slightly convex, produced at the lower end into a very narrow, short, imbedded disc, (or rather tooth,) which is itself a little curved downwards and blunt at the end.

Peduncle very narrow, about half as long as the capitulum; yellow, finely beaded, plainly ringed, without spines.

Mouth.—Labrum, with a row of minute teeth; palpi narrow. Mandibles with all the lower part narrow; of the four teeth, the second and third are narrow, the fourth is pectinated and placed very close to the inferior angle, which is produced into a long thin tooth. Maxillæ unknown.

Cirri.—First pair lost. The arrangement of the spines on all is most abnormal, Pl. X, fig. 29: dorsal tuft long, arranged in a transverse line and seated in a deep notch; in the sixth cirrus, the spines on the lower segments are fine, those on the upper segments are thick and claw-like, mingled with some fine spines; in the four anterior cirri the spines of the dorsal tufts are even thicker and more claw-like. On the anterior faces, also, of all the segments the spines form a single row; they are shorter than those composing the dorsal tuft; hence the spines on each segment are arranged in a circle, interrupted widely on the two sides: this arrangement is common to all five posterior cirri. Second cirrus, with the anterior ramus one third longer and thinner than the posterior ramus (this is the reverse of the usual arrangement); this longer ramus equals in length the sixth cirrus. Third cirrus, with the anterior ramus considerably longer than the posterior ramus; in the three posterior pair of cirri, also, the anterior rami are a little longer than the posterior: except in length, there is little difference of any kind between the five posterior pair of cirri. Pedicels of the cirri long; rami rather short; segments elongated, not protuberant.

Caudal Appendages nearly as long as the pedicels of the sixth cirrus, thickly clothed with very fine bristles, like a camel’s-hair pencil brush.

Affinities.—In the structure of the carina, and more especially of the scuta, there is a strong affinity between the present and following species; for we shall immediately see that in P. eburnea there is evidence of the scuta being composed of two segments fused together; and the larger segment is furnished with an internal oblique, strong, basal rim. To this same species there is an evident affinity in the form of the mandibles and of the caudal appendages, and in the anterior rami of the cirri being longer than the posterior rami. Notwithstanding these points of affinity, I consider that P. fissa is more closely related in its whole organisation, as more particularly shown in the arrangement of the spines on the cirri and in the presence of terga, to P. crassa than to P. eburnea. Although in Dichelaspis, the scuta are invariably composed of two almost separate segments, yet P. fissa shows no special affinity to this genus.

5. Pæcilasma eburnea. Pl. II, Fig. 5.

Trilasmis eburnea. Hinds. Voyage of Sulphur, 1844, vol. i, Mollusca, Pl. xxi, fig. 5.

P. valvis 3; scutis acuminatis, ovatis; ad pedunculum pæne transversè spectantibus; dentibus internis umbonalibus fortibus: tergis nullis: carinæ termino basali in discum amplum oblongum infossum producto.

Valves 3; scuta pointed, oval, placed almost transversely to the peduncle; internal umbonal teeth strong: terga absent: carina with the basal end produced into a large, oblong, imbedded disc.

Spines on the upper segments of the posterior cirri, arranged in three or four approximate longitudinal rows, making small brushes.

Habitat.—New Guinea, attached to the spines of a dead Echinus. Brit. Mus., and Cuming.

General Appearance.—Capitulum flat, pear-shaped, placed almost transversely to the peduncle. Valves white, smooth, moderately thick.

Scuta: the basal margin, as seen externally, is narrow, and can hardly be separated from the carinal margin; but an internal basal rim, (fig. 5, b) (along which the imbedded disc of the carina runs,) shows where, in the other species, the basal and carinal margins are separated. This basal internal rim is not parallel to the external basal margin, but runs upwards to the occludent margin, leaving beneath it a large triangular space, to which the membrane of the peduncle is attached; and this makes it appear as if the rostral umbones of these valves had grown downwards; but, judging from the allied species, P. fissa, I have no doubt that the primordial valves really lie on the umbones, and that the growth has been in the usual direction, that is, exclusively upwards. The occludent margin is curved, and blends by a regular sweep into the carinal margin, so that there is no acute upper angle. A distinct line can be seen, as if two calcareous valves had been united, running from the umbo to the upper end of the valve, thus in appearance separating a slip of the occludent margin; internally this appearance is more conspicuous; this structure is important in relation to that of P. fissa. The pointed umbones are divergent, and internally under each, there is a large tooth. The two valves are equally convex.

Terga, entirely absent.

The Carina (Tab. II, fig. 5, a, c), including the disc, is three fourths as long as the scuta; it is placed almost transversely to the longitudinal axis of the peduncle; it is narrow and internally convex; the imbedded disc is very large, forming a continuous curve with the upper part of the carina; this disc runs along the internal basal rim of the scuta, and hence almost separates, internally, the peduncle from the capitulum; it equals one fourth of the total length of the valve, and is thrice as wide as the upper part; it is oval, externally marked by a central line, and with a slight notch at the end, giving a divided appearance to the whole, and indicating how easily a fork might be formed from it. The carina is thick, measured from the inner convex to the exterior surface, which is carinated; heel prominent.

Peduncle, narrow, very short, not nearly so long as the capitulum.

Mouth.—Labrum considerably bullate, with the lower part much produced towards the adductor muscle; crest with small bead-like teeth; palpi small, pointed; mandibles, with the first tooth standing rather distant from the second; inferior angle spine-like and bifid; maxillæ (Pl. X, fig. 15), with two considerable spines (only one is shown in the Plate) beneath the upper large pair; the inferior upraised part bears seven or eight pair of spines, and its edge is not quite straight; close to the main notch, lying under the four upper spines, there are two minute notches, with the interspace bearing a tuft of fine spines and a pair of larger ones.

Cirri.—The rami in all are rather unequal in length, the anterior rami being rather the longest; the anterior rami of the second and third cirri are not thicker than the posterior rami. The segments in the three posterior cirri are not protuberant; the upper segments bear three or four pair of spines, with some minute intermediate ones, and with the lateral marginal spines unusually large and long, so as to form, with the ordinary pairs, a third or fourth longitudinal row; hence a small brush is formed on each segment. The dorsal tuft is large and wide, so as to contain even fourteen spines, of which some are as long as those in front. In the lower segments of these same posterior cirri, the lateral marginal spines are not so much developed (nor is the dorsal tuft), and hence the segments can hardly be said to be brush-like. The first cirrus is placed rather distant from the second pair. The second and third cirri differ from the three posterior pair, only in the bristles being slightly more numerous, and in the dorsal tufts being more spread out.

Caudal Appendages about half the length of the lower segments of the pedicels of the sixth cirrus; truncated and rounded at their ends; thickly clothed with long excessively fine bristles, so as to resemble camel-hair pencils.

The Stomach, I believe, is destitute of cæca; in it was a small crustacean.

General Remarks.—I was at first unwilling to sacrifice Mr. Hind’s genus, Trilasmis, which is so neatly characterised by its three valves; moreover, the present species does differ, in some slight respects, from the other species of Pæcilasma; but under the head of P. fissa I have shown how that species, P. crassa and P. eburnea are tied together. The absence of terga, which are rudimentary in P. crassa, (and we shall hereafter see, in Conchoderma, how worthless a character their entire absence is,) and the arrangement of the spines in the upper segments of the posterior cirri, are the only characters which could be used for a generic separation.

Genus—Dichelaspis. Plate II.

Octolasmis.[32] J. E. Gray. Annals of Philosophy, vol. x, new series, p. 100, August 1825.

Heptalasmis. Agassiz. Nomenclator Zoologicus.

Valvæ 5, quæ ferè pro septem haberi possent, scuto in segmenta planè duo, ad angulum autem rostralem conjuncta, diviso: carina plerumque sursum inter terga extensa, deorsum aut disco infosso aut furcâ aut calyce terminata.

Valves 5, generally appearing like 7, from each scutum being divided into two distinct segments, united at the rostral angle; carina generally extending up between the terga terminating downwards in an imbedded disc, or fork, or cup.

Mandibles, with three or four teeth; maxillæ notched, with the lower part of edge generally not prominent; anterior ramus of the second cirrus not thicker than the posterior ramus, not very thickly clothed with spines; caudal appendages uniarticulate, spinose.

Distribution.—Eastern and Western warmer oceans in the Northern hemisphere, attached to crustacea, sea-snakes, &c.

Description.—The capitulum appears to contain seven valves; but, on examination, it is found that two of the valves on each side, are merely segments of the scutum; these are united at the umbo, in three of the species, by a narrow, non-calcified portion of valve, where the primordial valve is situated; in D. orthogonia, however, the junction of the two segments is perfectly calcified, and of the same width as the whole of the basal segment. The capitulum is much compressed, broad at the base, and extends a little beneath the basal segments of the scuta. The valves are very thin, often imperfectly calcified, and generally covered with membrane. They are not placed very close together, and in all the species a considerable interspace is left between the carina and the two other valves: in the D. Grayii the valves are so narrow that they form merely a calcified border round the capitulum. The membrane between the valves and over them, is very thin, and is thickly studded, in some of the species, with minute blunt conical points, apparently representing spines. The valves in the same species present considerable variations in shape; in their manner or direction of growth, and in the position of their primordial valves, they agree with Lepas and Pæcilasma.

Scuta.—In three of the species the two segments, named the occludent and basal, appear like separate valves, but these, by dissection, can be most distinctly seen to be united at the rostral angle. The primordial valve, formed of the usual hexagonal tissue, is elliptic, elongated, and placed in the direction of the occludent segment; calcification commences at its upper point, so as to form the occludent segment, and afterwards at its lower point, but rectangularly outwards, to form the basal segment; in the minute space between these two points of the primordial valve, there is, in four of the species, no calcification; so that the two segments are united by what may be called a flexible hinge; in D. orthogonia the two calcareous segments are absolutely continuous. The occludent segment is longer than the basal segment; it either runs close along the orifice, or in the upper part bends inwards; both segments are narrow, except in D. Warwickii, in which the basal segment is moderately broad; the two segments are placed at an angle, varying from 45° to 90°, to each other. The capitulum generally extends for a little space beneath the basal segments of the scuta, where it contracts to form the peduncle.

The Terga present singular differences in shape, and are described under the head of each species; scarcely any point can be predicated of them in common, except that they are flat and thin.

The Carina is much bowed, narrow, and internally either slightly concave or convex and solid; the upper end extends far up between the terga; the lower end is formed by a rectangularly inflected, imbedded, triangular or oblong disc, deeply notched at the end, or as in H. Lowei, of a fork, the base, however, of which is wider than the rest of the carina, so as to present some traces of the disc-like structure of the other two species; or lastly, as in D. orthogonia, it terminates in a crescent-formed cup.

Peduncle.—This is narrow, compressed, and about as long, or twice as long, as the capitulum; in D. Warwickii it is studded with minute beads of yellowish chitine.

Size.—Small, with a capitulum scarcely exceeding a quarter of a inch in length.

Filamentary Appendages.—None. There are two small ovigerous fræna, which, in D. Warwickii, had the glands collected in seven or eight little groups on their margins.

Mouth.—Labrum highly bullate, with small teeth on the crest; palpi small, not thickly covered with spines. Mandibles narrow, with three or four teeth. Maxillæ small, with a notch beneath the two or three great upper spines; lower part bearing only a few pair of spines, generally not projecting, but in D. orthogonia largely projecting. Outer maxillæ, with their inner edges continuously covered with bristles.

Cirri.—First pair short, situated rather far from the second pair; second pair with the anterior ramus not thicker than the posterior ramus, and hardly more thickly clothed with spines than it, excepting sometimes the few basal segments. All the five posterior pair of cirri resemble each other more closely than is usual. In D. Lowei, the segments of the posterior cirri bear the unusual number of eight pair of main spines.

Caudal Appendages.—Uni-articulate, spinose; in D. pellucida they are twice as long as the pedicels of the sixth cirrus, but I could not perceive in them any distinct articulations.

Distribution.—Attached to crabs at Madeira, and off Borneo; to sea-snakes in the Indian Ocean. The individuals of all the species appear to be rare.

General Remarks.—Four of the five species, forming this genus, though certainly distinct, are closely allied. I have already shown, that although the characters separating Lepas, Pæcilasma, and Dichelaspis are not very important, yet if they be neglected these three natural little groups must be confounded together. Dichelaspis is much more closely united to Pæcilasma than to Lepas, and, as far as the more important characters of the animal’s body are concerned, there is no important difference between them. Consequently, I at first united Pæcilasma and Dichelaspis, but the latter forms so natural a genus, and is so easily distinguished externally, that I have thought it a pity to sacrifice it. The carina, (which seems to afford better characters than the other valves in Dichelaspis,) from generally running up between the terga and in ending downwards, in three of the species, in a deeply notched disc or fork, more resembles that in Lepas than in Pæcilasma; in the manner, however, in which the imbedded disc, in D. Warwickii and D. Grayii, nearly cuts off the inside of the capitulum from the peduncle, there is a resemblance to Pæcilasma eburnea. In the extent to which the valves are separated from each other, in the bilobed form of the scuta, (the two segments in Dichelaspis, perhaps, answering to the upper and lateral projections in the scuta of Conchoderma virgata,) and in the basal half of the scuta not descending to the base of the capitulum, there is a considerable resemblance to Conchoderma; in both genera the adductor muscle is attached under the umbones of the scuta; but the structure of the mouth and cirri and caudal appendages shows that the affinity is not stronger to Conchoderma than to Lepas. It appears at first probable, that Dichelaspis would present a much closer affinity to Pæcilasma fissa, in which, owing to the scuta being formed of two segments, there are seven valves, than to any other species of that genus; but in P. fissa the primordial valve is triangular and is situated on the basal segment, whereas, in Dichelaspis, it is elliptic and is seated between the two segments, and is more in connection with the occludent than with the basal segment; and this I cannot but think is an important difference: in other respects, P. fissa shows no more affinity to Dichelaspis than do the other species of the genus. Finally, I may add that Dichelaspis bears nearly the same relation to Pæcilasma, as Conchoderma does to Lepas.

1. Dichelaspis Warwickii. Pl. II, figs. 6, 6 a, b.

Octolasmis Warwickii. J. E. Gray. Annals of Philosophy, vol. x, p. 100, 1825; Spicilegia Zoologica. t. vi, fig. 16, 1830.

D. scutorum segmento basali duplo latiore quam segmentum occludens: tergorum parte inferiore paulò latiore quam occludens scutorum segmentum.

Scuta, with the basal segment twice as wide as the occludent segment; terga, with the lower part slightly wider than the occludent segment of the scuta.

Mandibles, generally with four teeth.

Off Borneo, attached to a crab (Belcher): China Sea. British Museum.

General Appearance.—Capitulum much compressed, elongated, with the valves not very close together, the carina being separated by a rather wide space from the scuta and terga. Valves variable in shape, very thin and translucent, covered by thin membrane, which, over the whole capitulum, is studded with minute blunt points.

Scuta.—Segments without internal teeth or an internal basal rim; the occludent segment long, narrow, pointed, not quite flat, sometimes slightly wider in the upper part; about one third of its own length longer than the basal segment; occludent margin slightly arched; basal segment about twice as wide as the occludent segment, triangular, slightly convex; in young specimens (Pl. II, fig. 6 b), the carinal margin of the basal segment is protuberant, and the occludent margin hollowed out; in old specimens the occludent margin of the basal segment is straight, and the carinal margin much hollowed out. In very young specimens the basal segment is very small compared to the occludent.

Terga, variable in shape; flat, lower part wider than the occludent segment of the scuta; occludent margin double, forming a considerable rectangular projection, as in the terga of Lepas; scutal margin deeply excised at a point corresponding with the apex of the scuta, a flat tooth or projection being thus formed; there is sometimes a second tooth (fig. 6 b) a little above the basal point. The terga, in the first variety, somewhat resemble in shape the scuta of Conchoderma aurita.

Carina, much bowed, narrow, slightly concave within, (in the Borneo specimen, rather wider and more concave,) extending up between the terga for half their length, terminating downwards in a rectangularly inflected, deeply imbedded, oblong, rather wide, flat disc, at its extremity more or less deeply notched. This disc is externally smooth; internally it sometimes has two divergent ridges on it; it extends across about two-thirds of the base of the capitulum (fig. 6 a, as seen from beneath, when the peduncle is cut off), to under the middle of the basal segments of the scuta.

Peduncle, narrow, flattened; united to the capitulum some little way below the scuta; about as long as the capitulum; the membrane of which it is composed is thin, externally studded with bluntly conical beads of yellowish chitine, of which the largest were 1/2000 of an inch in diameter; on their internal surfaces these are furnished with a small central, circular depression, apparently for a tubulus; the arrangement of the beads varied in concentric zones. Similar conical points on the capitulum have an internal concave surface about 1/3000 in diameter, with a central circle 1/12000 in diameter, for the insertion, as I believe, of a tubulus.

Size.—The largest specimen had a capitulum a quarter of an inch long.

Mouth.—Labrum highly bullate; crest with not very minute, blunt teeth, which towards the middle lie closer and closer to each other, so as to touch. Palpi rather small, with a few very long bristles at the apex.

Mandibles, narrow, produced, with four teeth, and the inferior angle tooth-like and acuminated; in one specimen, on one side of the mouth, the mandible had only three teeth.

Maxillæ, small; at the upper angle there are two large spines and a single small one, beneath which there is a deep notch, and beneath this a straight but projecting edge, bearing a few moderately large and some smaller spines. Outer maxillæ sparingly covered with bristles along the inner margin.

Cirri.—First pair far removed from the second pair, and not above half their length; segments rather broad, with transverse rows of bristles not very thickly crowded together; terminal segments very obtuse, and furnished with thick spines. The segments of the three posterior pair have each three or four pair of spines, with a few minute spines scattered in an exterior, parallel, longitudinal row; dorsal tufts, with four or five long spines. The second cirrus has its anterior ramus not thicker, but rather shorter than the posterior ramus; the former is only a little more thickly clothed with spines, owing to those in the longitudinal lateral row being longer and more numerous, than is the sixth pair of cirri. Bristles not serrated.

Caudal Appendages, narrow, thin, slightly curved, about half as long as the pedicels of the sixth cirrus; in young specimens, the appendage bore seven or eight pair of long bristles rectangularly projecting; in some older specimens, there was a tuft of bristles on the summit, and two other tufts on the sides.

I at first thought that the Borneo specimen was a distinct species, but after careful comparison of the external and internal parts, the only difference which I can detect is, that the terga are slightly larger, and that the carina, to a more evident degree, is wider, more especially in the middle and lower portions.

2. Dichelaspis Grayii. Pl. II, fig. 9.

D. scutorum segmento basali angustiore quam segmentum occludens; longitudine pæne dimidiâ: tergis bipenniformibus, margine crenato, spinâ posticâ, manubrio angustiore quam occludens scutorum segmentum.

Scuta, with the basal segment narrower than the occludent segment, and about half as long as it. Terga like a battle-axe, with the edge crenated and a spike behind; the handle narrower than the occludent segment of the scuta.

Mandibles with three teeth; cirri unknown.

Attached to the skin of a sea-snake, believed to have been the Hydeus or Pelamis bicolor, and therefore from the Tropical, Indian or Pacific Oceans; associated with the Conchoderma Hunteri; single specimen, in a very bad condition, in the Royal College of Surgeons.

General Appearance.—Capitulum much compressed, elongated, formed of very thin membrane, with the valves forming round it a mere border. Valves thin, imperfectly calcified, covered with membrane.

Scuta formed of two narrow plates at very nearly right-angles to each other, one extending along the occludent, and the other along the basal margin; both become very narrow at the point of junction, and are there not calcified, but are evidently continuous and form part of the same valve; the basal segment is about half as long and narrower than the occludent segment, flat and bluntly pointed at the end; occludent segment slightly curled, and therefore the whole does not lie quite in the same plane; narrow close to the umbo, with a very minute tooth on the under side; apex rounded. In the upper part, the occludent segments leave the membranous margin of the orifice, and run in near to the terga, bending towards them at an angle of 45° with their lower part. I was unable to distinguish the primordial valves.

Terga.—These valves are of the most singular shape, resembling a battle-axe, with a flat and rather broad handle; the upper part consists of an axe, with a broad cutting crenated edge, behind which is a short blunt spike. The spike and cutting edge together answer to the double occludent margin of the tergum in Lepas. The whole valve is flat, thin, and lies in the same plane; the carinal margin is nearly straight; the scutal margin bulges out a little, and at a short distance above the blunt basal point is suddenly narrowed in, making the lowermost portion very narrow; the widest part of the handle of the battle-axe, is narrower than the occludent segment of the scuta. The two spikes behind the cutting and crenated edges of the two terga, are blunt and almost touch each other; above their point of juncture, the membrane of the orifice forms a slight central protuberance.

Carina, very narrow throughout, concave within, much bowed; upper point broken and lost, but it must have run up between the terga for more than half their length; basal portion inflected at nearly right angles, and running in between, and close below, the linear basal segments of the scuta, so as almost entirely to cut off internally the peduncle and capitulum. This lower inflected and imbedded portion, or disc, gradually widens towards its further end, which is, at least, four times as wide as the upper part of the carina, and is deeply excised, but to what exact extent I cannot state, as the specimen was much broken. On each side of this elongated triangular disc, there is a slight shoulder corresponding to the ends of the basal segments of the scuta; and on the upper surface of each shoulder, there is a small tooth or projection. The middle part of the disc is barely calcified, and is transparent.

Peduncle, rather longer than, and not above half as wide as, the capitulum; the latter being nearly 2/10ths of an inch in length: the membrane of the peduncle is thin, naked and structureless.

Mouth.—Labrum highly protuberant in the upper part, with a row of beads on the crest. Palpi small, with few bristles. Mandibles, with the whole inferior part, very narrow; three teeth very sharp, with a slight projection, perhaps, marking the place of a fourth tooth; inferior angle ending in the minutest point; first tooth as far from the second, as the latter from the inferior angle. Maxillæ with a broad shallow notch; inferior angle much rounded, bearing only four or five pair of spines.

Cirri.—First pair apparently remote from the second pair; all five posterior pair lost; first pair short, with the rami unequal by about two segments; segments clothed with several transverse rows of bristles; terminal segments blunt.

3. Dichelaspis pellucida. Pl. II, fig. 7.

D. valvarum singularum acuminibus superioribus et inferioribus vix intersecantibus: scutorum segmento basali multo angustiore quam segmentum occludens; longitudine ferè dimidiâ: tergis bipenniformibus, margine integro, manubrii acumine ad carinam flexo.

Valves with the upper and lower points of the several valves only just crossing each other. Scuta with the basal segment much narrower than the occludent segment, and about half as long as it. Terga like a battle-axe, with the edge smooth, and the point of the handle bent towards the carina.

Mandibles with four teeth; caudal appendages twice as long as the pedicels of the sixth cirrus.

Indian Ocean; attached to a sea-snake.

This species comes very close to the D. Grayii, which likewise was attached to a snake; but I cannot persuade myself, without seeing a graduated series, that the differences immediately to be pointed out can be due to ordinary variation. I am much indebted for specimens to the kindness of Mr. Busk.

General Appearance.—The membrane of the capitulum and peduncle is surprisingly thin and pellucid, so that the ovarian tubes within the peduncle can be traced with the greatest ease. The valves are small, the apices only just crossing each other, and are composed of yellow chitine, with mere traces of calcification. The capitulum is pointed, oval, .15 of an inch long; the peduncle is narrow, and fully twice as long as the capitulum.

Scuta.—The two segments stand at right-angles to each other; the basal segment is linear and pointed, fully half as long, but only one third as wide, as the occludent segment. The point of junction of the two segments is wider than the rest of the basal segment. This latter segment lies some little way above the top of the peduncle. The occludent segment is bluntly pointed; it is directed a little inwards from the edge of the orifice towards the terga; the apex reaches up just above the slightly reflexed lower point of the terga. The adductor muscle is fixed under the point of junction of the two segments.

The Terga are battle axe-shaped, with the blade part very prominent, smooth-edged; behind the blade there is a short upwardly-turned prominence. The lower point of the handle of the axe, is bent towards the carina. The tergum, measured in a straight line, equals in length two thirds of the occludent segment of the scutum, the handle being rather narrower than this same segment.

The Carina is extremely narrow and much bowed; the apex reaches up only to just above the lower bent points of the terga. The basal end is rectangularly inflected, and stretches internally nearly across the peduncle; it consists (fig. 7 a) of a triangular disc of yellow thin membrane, four or five times as wide as the upper part of the valve; the end of this disc is hollowed out; its edges are thickened and calcified, and hence, at first, instead of a disc, this lower part of the carina appears like a wide fork; the tips of the prongs stretch just under the tips of the basal segments of the scuta.

Peduncle.—Its narrowness and transparency are its only two remarkable characters.

Mouth.—All the parts closely resemble those of D. Grayii, but being in a better state of preservation I will describe them. The labrum is highly bullate, with a row of minute teeth on the crest, placed very close together in the middle. Palpi small, thinly clothed with spines; mandibles extremely narrow, hairy, with four teeth, but the lower tooth is so close to the inferior angle, as only to make the latter look double. Maxillæ, with a very deep broad notch, dividing the whole into two almost equal halves; in the upper part there are three main spines.

Cirri.—The first pair are placed at a considerable distance from the second pair; they are short with equal rami, and rather broad segments furnished with a few transverse rows of bristles. The five posterior cirri have singularly few, but much elongated segments, bearing four pair of spines: the two rami of the second pair are alike, and differ only from the posterior cirri in a few of the basal segments having a few more spines.

The Caudal Appendages are twice as long as the pedicels, and nearly half as long as the whole of the sixth cirrus; they have a small tuft of long thin spines at their ends, and a few in pairs, or single, along their whole length; at first I thought that they were multi-articulate, but after careful examination I can perceive no distinct articulations; I have seen no other instance of so long an appendage without articulations.

Diagnosis.—This species differs from D. Grayii in all the valves being shorter, so that their points only just cross each other; but this, I conceive, is an unimportant character. In the scuta, the basal segment is here narrower, but the point of junction of the two segments wider than in that species; in the terga, the edge of the axe is smooth instead of being crenated, and the handle and the point behind are of a rather different shape; in the carina the imbedded basal disc has not shoulders and small teeth, as in D. Grayii. Notwithstanding these differences, I should not be much surprised if the present form were to turn out to be a mere variety.

4. Dichelaspis Lowei. Pl. II, fig. 8.

D. scutorum segmento basali angustiore quam occludens segmentum, longitudine ferè 4/5: tergorum parte inferiori duplo latiore quam occludens scutorum segmentum.

Scuta with the basal segment narrower than the occludent segment, and about four-fifths as long as it. Terga with the lower part twice as wide as the occludent segment of the scuta.

Mandibles with four teeth; segments of the three posterior cirri with eight pair of main spines.

Hab.—Madeira; attached to a rare Brachyourous Crab, discovered by the Rev R. T. Lowe. Very rare.

General Appearance.—Capitulum much compressed, sub-triangular, formed of very thin membrane; valves imperfectly calcified, and thin.

Scuta formed of two narrow plates placed at about an angle of 50° to each other, and united at the umbo by a non-calcified flexible portion. The primordial valve is situated at this point, but chiefly on the occludent segment. The occludent segment is about twice as wide and about one fifth longer than the basal segment, which latter is rather sharply pointed at its end. The occludent segment is slightly arched, a little narrowed in on the occludent margin close to the umbo; its upper end is broad and blunt; it runs throughout close to the edge of the orifice of the sack, and its longer axis is in the same line with that of the terga. Close to the umbones, on the under side of the basal segment, there is, on each valve, a longitudinal calcified fold, serving as a tooth.

Terga broad, with a deep notch corresponding to the apex of the occludent segment of the scuta; the part beneath the notch is of nearly the same width throughout, and is twice as broad as the occludent segment of the scuta; it has its basal angle very broad and blunt. The entire length of the terga equals two thirds of that of the occludent segment of the scuta; occludent margin simply and slightly curved.

The Carina is of nearly the same width throughout, with the upper part rather the widest, and the apex blunt; within convex; it extends up between three fourths of the length of the terga, terminating downwards in a fork with very sharp prongs, standing at right-angles to each other (fig. 8 a.) The fork, measured from point to point, is thrice as wide as, and measured across at the bottom of the prongs it is wider than, the widest upper part of the valve,—a resemblance being thus shown with the triangular notched disc in D. Grayii. The points of the prong extend under about one fourth of the length of the basal segments of the scuta.

Peduncle rather longer than the capitulum, which, in the largest specimen, was 2/10ths of an inch in length; peduncle narrow, close under the capitulum; membrane thin and structureless. The larger specimen had almost mature ova in the lamellæ.

Mouth.—Labrum with a few bead-like teeth on the crest, distant from each other even in the central part; palpi rather small, moderately clothed with bristles.

Mandibles, with four teeth; the inferior angle blunt and broad, showing, apparently, a rudiment of a fifth tooth; the first tooth is as far from the second, as is this from the inferior angle; second, third, and fourth teeth very blunt, whole inferior part of mandible not much narrowed. Maxillæ small, with a small notch under the three upper spines, which are followed by five or six pair, nearly as large as the upper spines.

Cirri.—First pair remote from the second; their rami nearly equal, and about one third of the length of the rami of the second cirrus; thickly clothed with bristles: rami of the second cirrus of equal thickness, but little shorter than those of the sixth cirrus; the three or four basal segments of the anterior ramus are thickly clothed with spines; the other segments, and all the segments on the third pair, resemble the segments of the three posterior pair. These latter are elongated, not protuberant, and support eight pairs of spines with very minute intermediate spines; those in the dorsal tufts are numerous and long.

Caudal Appendages nearly as long as the pedicels of the sixth cirrus; oval, moderately pointed, with their sides, for one fourth of their length, thickly clothed with long very thin spines.

Affinities.—In the form of the scuta and of the carina this species is most nearly allied to D. Grayii or D. pellucida, in the form of the terga to D. Warwickii.

5. Dichelaspis orthogonia. Pl. II, fig. 10.

D. scutorum basali segmento angustiore quam occludens segmentum; longitudine ferè dimidiâ; duorum segmentorum junctione calcareâ: tergorum prominentiis marginalibus inæqualibus quinque: carinâ deorsum in parvo calyce lunato terminatâ.

Scuta with the basal segment narrower than the occludent segment, and about half as long as it; junction of the two segments calcified. Terga with five unequal marginal projections. Carina terminating downwards in a small crescent-formed cup.

Maxillæ with the inferior part of edge much upraised.

Hab. unknown; associated with Scalpellum rutilum, apparently attached to a horny coralline. British Museum.

The specimens are in a bad condition, not one with all the valves in their proper positions, and most of them broken; animal’s body much decayed and fragile.

General Appearance.—Capitulum apparently much flattened; valves naked, coloured reddish, separated from each other by thin structureless membrane.

The Scuta consist of two bars placed at right-angles to each other, with the point of junction fully as wide as any part of the basal segment, and perfectly calcified; the primordial valve lies at the bottom of the occludent segment. The basal segment is equally narrow throughout, and very slightly concave within; the occludent segment widens a little above the junction or umbo, and then keeps of the same width to the apex, which is obliquely truncated; internally this segment is concave; externally it has a central ridge running along it; the occludent segment is twice as long and twice as broad as the basal segment. Both segments are a little bowed from their junction to their apices.

Terga.—These are of a singular shape; they are about three-fourths as long as the occludent segment of the scuta, and in their widest part, of greater width than it. They consist of four prominent ridges proceeding from the umbo, and united together for part only of their length, and, therefore, ending in four prominences; one of these, the longest, has the same width throughout, and forms the basal point; a second, very small one, is seated high up on the carinal margin just above the apex of the carina; the third and fourth, are nearly equal in length, and project one above the other on the scutal margin. There are two occludent margins, meeting each other at right angles, and forming a prominence, as in Lepas; and this gives to the margin of the valve the five prominences. The whole valve internally is flat; externally, it is ridged as described.

Carina (fig. 10, a, b), much bowed, narrow, long; externally, the central ridge is quite flattened; internally, slightly concave, but scarcely so towards the lower part, which is narrow; the upper part widens gradually, and the apex is rounded. The basal embedded portion is as wide as the uppermost part, and forms a cup, unlike anything else known: the outline of this cup is semi-oval and crescent-formed; it is moderately deep; it is formed by the external lamina of the carina bending rectangularly downwards and a little outwards, whereas the inner lamina of the lower part (which is slightly concave), is continued with the same curve as just above, and forms the concave chord to the semi-oval rim of the cup. This cup, I believe, lies under the points of the basal segments of the scuta.

Peduncle unknown, probably short.

Length of capitulum, above 2/10ths of an inch.

Mouth.—Labrum with the upper part highly bullate, and produced into a large overhanging projection; crest with a row of rather large bead-like teeth; palpi small, their two sides parallel, very sparingly covered with long bristles.

Mandibles, narrow, produced, with four teeth, and the inferior angle produced into a single strong spine: the distance between the tips of the first and second teeth almost equals that between the tip of the second tooth and of the inferior angle.

Maxillæ with three large upper unequal spines, beneath which, there is a deep and wide notch (bearing one spine), and the inferior part projects highly, bearing three or four pairs of spines, and is, itself, obscurely divided into two steps.

Outer Maxillæ, very sparingly covered with bristles; outline, hemispherical.

Cirri.—The rami of the five posterior pair are extremely long, as are the pedicels; the segments are much elongated, with their anterior faces not at all protuberant; each bears five pair of very long and thin spines, with an excessively minute one between each pair; the dorsal tuft consists of very fine and thin spines. The second cirrus has its anterior ramus not at all thicker than the posterior ramus; but has an exterior third longitudinal row of small bristles. First cirrus, separated by a wide interval from the second pair; very short with the two rami slightly unequal in length; the segments are broad, and are paved moderately thickly with spines; the terminal spines not particularly thick.

Caudal Appendages consist of very small and narrow plates, about half the length of the pedicels of the sixth cirrus, with a few long spines at their ends.

This well-marked species, I think, has not more affinity to one than to another of the previous species: it differs from all, in the junction between the two segments of the scuta being perfectly calcified; in the peculiar cup, forming the base of the carina; and lastly, in the inferior part of the maxillæ projecting.

Oxynaspis.[33] Gen. Nov. Pl. III.

Valvæ 5, approximatæ: scutorum umbones in medio marginis occludentis positi: carina rectangulè flexa, sursùm inter terga extensa, termino basali simpliciter concavo.

Valves 5, approximate; scuta with their umbones in the middle of the occludent margin; carina rectangularly bent, extending up between the terga, with the basal end simply concave.

Mandibles with four teeth; maxillæ notched, with the lower part of edge nearly straight, prominent; anterior ramus of the second cirrus thicker than the posterior ramus; caudal appendages, uniarticulate, spinose.

Attached to horny corallines.

I have most unwillingly instituted this genus; but it will be seen by the following description, that the one known species could not have been introduced into Lepas or Pæcilasma, without destroying these genera, although it has a close general resemblance with both. As far as the valves are concerned, it is more nearly related to Lepas than to Pæcilasma; but taking the entire animal, its relation is much closer to the latter genus than to Lepas: it differs from both these genera in the manner of growth of the scuta, which is both upwards and downwards, the primordial valve being situated in nearly the middle of the occludent margin. In this respect, and in the shape of the carina and terga, there is an almost absolute identity with Scalpellum; I may, however, remark that in Scalpellum, the scuta first grow downwards, and afterwards in most of the species upwards, whereas here from the beginning, the growth is both upwards and downwards. In the mouth and cirri, there is rather more resemblance to Scalpellum than to Pæcilasma and Lepas: in habits, also, this genus agrees with Scalpellum, and if it had possessed a lower whorl of valves, it would have quite naturally entered that genus. It is unfortunate, that so insignificant and poorly characterised a form should require a generic appellation. In natural position, it appears to lead from Scalpellum through Pæcilasma to Lepas.

1. Oxynaspis celata. Pl. III, fig. 1.

Madeira; attached in numbers to an Antipathes; Rev. R. T. Lowe. Mus., Hancock.

General Appearance.—The capitulum is rather thin, and broad in proportion to its length; it seems always entirely covered by the horny muricated bark of the Antipathes, and hence externally is coloured rich brown and covered with little horny spines. The membrane over the valves is very thin, and is with difficulty separated from the Antipathes; it has, I believe, no spines of its own. The corium lining the peduncle is a fine purple. All the individuals are attached to the coralline, with their capitulums upwards in the direction of the branches, and in this respect fig. 1. is erroneous.

The valves, when cleared of the bark, are white, or are strongly tinged with pinkish-orange. The upper parts of the scuta and terga are plainly furrowed in lines radiating from their umbones; hence their margins are serrated with blunt teeth; their surfaces, moreover, are sparingly studded with small calcareous points.

Scuta (fig. 1, a), sub-triangular, with the lower part rounded and protuberant, the upper produced and pointed. The umbo is situated in the middle of the occludent margin, instead of at the rostral angle, as in the foregoing genera. The occludent margin is straight, and is bordered by a narrow step or ledge, formed of transverse growth-ridges, and therefore has its edge serrated: the rostral angle is often slightly produced into a small projection. The basal margin is short, and forms an angle above a rectangle with the occludent margin: the tergal margin is straight; the carinal margin is rounded, protuberant, and of unusual length compared to the basal margin. The surface of the valve is convex near the umbo; and beneath there is a large deep hollow for the adductor muscle.

Terga (fig. 1, b) large, flat, triangular, as long as the scuta or the carina, all three valves being nearly equal in length; occludent margin straight, or slightly arched, basal angle broad, not very sharp.

Carina short (fig. 1, c, drawn rather too long), deeply concave, rectangularly bent, with the lower part not quite as long as the upper, and a little wider: the basal margin is truncated, rounded, and slightly sinuous. The umbo is situated at the angle, and therefore nearly central. The umbo of the terga, I may add, is in the same place, as in Lepas.

The peduncle is very short and narrow, and is, I believe, without spines; it is enveloped by the bark of the Antipathes. The capitulum in the largest specimens was .2 of an inch in length.

Filamentary Appendages, apparently none.

Mouth, with the orifice rather inclined abdominally.

Labrum, with the upper part extremely protuberant, forming a projecting horn; no teeth on the crest. Palpi rather small, with only a few bristles at the end.

Mandibles, with four teeth and the inferior angle pointed: first tooth as far from the second, as is the latter from the inferior angle; in one specimen, on one side, there were five teeth.

Maxillæ with three great spines at the upper angle, beneath which a deep notch, and with the inferior part much upraised; this lower part rather rounded at both corners, with the upper spines longer than the lower.

Outer Maxillæ, with the bristles continuous in front; externally, slightly protuberant, with a tuft of bristles longer than those on the front side. Olfactory orifices apparently not protuberant; but all the specimens were in a bad state.

Cirri.—Prosoma very little developed. First cirrus very far removed from the second. The three posterior cirri are straight and long; the segments are elongated and bear four or five pairs of very long spines, with a single minute intermediate spine between each pair; dorsal tufts, with long spines. First cirrus, rami unequal by two or three segments, and thickly covered with spines; the first cirrus is short compared to the second, owing to the length of the pedicel of the latter, though the longer ramus of the first, nearly equals the shorter ramus of the second pair. Second cirrus, with its anterior ramus shorter by two or three segments than the posterior ramus, and thicker than it, with the segments covered like brushes with bristles; posterior ramus, and both rami of the third cirrus, a little more thickly clothed with bristles than are the three posterior cirri.

Caudal Appendages, minute, broadly oval, with six or seven long bristles on their summits.

Genus—Conchoderma. Plate III.

Conchoderma. Olfers. Magaz. der Gesellsch. Natuforsch. Freunde zu Berlin, Drittes Quartel, 1814.[34]

Lepas. Linnæus. Systema Naturæ, 1767.

Branta. Oken. Lehrbuch der Naturgeschichte, Th. 2, p. 362, 1815.

Malacotta et Senoclita. Schumacher. Essai d’un Nouveau Syst. des Habitations des Vers., 1817.

Otion et Cineras. Leach. Journal de Phys., vol. lxxxv, p. 67, July, 1817.

Gymnolepas. De Blainville. Dict. des Sci. Nat., Art. Mollusca, 1824.

Pamina. J. E. Gray. Annals of Philosophy, vol. x, (Second Series,) August, 1825.[35]

Valvæ 2 ad 5, minutæ, inter se remotæ: scuta bi-aut tri-lobata, umbonibus in medio marginis occludentis positis: carina arcuata, terminis utrinque pæne similibus.

Valves 2 to 5, minute, remote from each other: scuta with two or three lobes, with their umbones in the middle of the occludent margin: carina arched, upper and lower ends nearly alike.

Filaments seated beneath the basal articulations of the first pair of cirri, and on the pedicels of four or five anterior pairs; mandibles, with five teeth, finely pectinated; maxillæ step-formed; caudal appendages, none.

Distribution.—Mundane, throughout the equatorial, temperate, and cold seas; attached to floating objects, living or inorganic.

The Capitulum is formed of smooth membrane, including five small valves, of which the terga and carina are often quite rudimentary or absent. Valves minute, thin, generally more or less linear, placed far distant from each other; sometimes imperfectly calcified and covered by chitine membrane, or imbedded in it. The umbones of the valves (together with the primordial valves) are nearly central, so that they are added to at their upper and lower ends; hence their manner of growth is considerably different from that of the valves in Lepas. The adductor muscle is attached to a slight concavity on the under side of each scutum, at the point whence the lobes diverge.

The Terga are placed almost transversely to the scuta; at their lower ends, there is either a very slight prominence in the capitulum, or there is a large tubular, folded appendage, opening into the sack, and apparently serving for respiratory purposes.

Peduncle, smooth, moderately long; attachment effected by the cement-stuff being poured out exclusively, as it appears, from the larval antennæ. These antennæ in C. aurita and C. virgata, resemble, in the form of the disc and in the long feathered spines on the ultimate segment, those in Lepas.

The Filamentary Appendages are highly developed; there are six or seven on each side; two are attached beneath the basal articulation of the first cirrus (as is usual in Lepas), and near them there are one or two small pap-formed projections of apparently similar nature; the rest of the filaments are attached to the posterior edges low down, on the lower segments of the pedicels of the cirri. I believe, in all cases, these appendages are occupied by testes.

Prosoma, moderately developed.

Mouth, situated not far from the adductor muscle; labrum considerably bullate, with the crest hairy and pectinated with inwardly pointing, approximate, flattened teeth: inner fold of the supra-œsophageal cavity slightly thickened and yellowish, villose on the sides.

Palpi of the usual shape, not meeting, moderately broad.

Mandibles, with five teeth, graduated in size, nearly equidistant, finely pectinated either on one or both sides towards their bases; inferior angle narrow, either produced into a fine tooth, or almost rudimentary.

Maxillæ, about 3/4ths of the size of the mandibles, step-formed, with five steps generally distinct; at the upper angle there are two large unequal spines, of which the lower one is the largest, with a third long thin one on the first step; lower spines doubly serrated. Apodeme directed inwards and backwards.

Outer Maxillæ (Pl. X, fig. 16) simply arched; the membrane of the supra-œsophageal cavity under these maxillæ is highly bullate and villose. Olfactory orifices not prominent.

Cirri.—First pair not seated far distant from the second pair. The three posterior pair have the anterior faces of their segments considerably protuberant, supporting four or five pairs of long bristles; between which, there is a row of minute, fine, upwardly pointing bristles: on the lateral upper margins of each segment, there are a few very minute spines; dorsal tuft short, with thick and thin spines intermingled. In the first cirrus (of which the rami are nearly equal in length), and in the anterior ramus of the second cirrus, the faces of the segments are highly protuberant, and clothed with thick transverse rows of finely and doubly serrated spines: the anterior ramus of the second cirrus is considerably thicker than the posterior ramus, which latter, together with both rami of the third cirrus, differ from the three posterior cirri only in the intermediate and in the lateral marginal spines being slightly more developed.

Caudal Appendages, absent.

Alimentary Canal.—The upper part of the stomach has four large cæca, of which the posterior one is the largest; the whole surface, also, is covered with minute pits, arranged in transverse rows.

Generative System, developed to an extraordinary degree. The testes run into all the filamentary appendages, as well as more or less, into the pedicels of the cirri: the two vesiculæ seminales unite within the penis, either just beyond its basal constriction, or up one third of its length. Penis short, hairy. The ovarian tubes not only fill the peduncle, but extend in a thin sheet between the two folds of corium all round the sack, close up to the terga. The two ovigerous fræna are present in the usual position; the ovigerous lamellæ either form several layers, in pairs, one under the other, or are united in a single large cup-formed sheet enclosing the whole animal.

Colours.—The prevailing tint is a dark purplish-brown, which forms, or tends to form, broad longitudinal bands on the peduncle and capitulum.

General Remarks.—This genus is intimately related, as has been remarked by Professor Macgillivray,[36] to Lepas: if we look to the body of the animal, which from being less exposed to external influences must, in the Cirripedia, offer the most trustworthy characters, we find that in Conchoderma there are additional filamentary appendages attached to the cirri, that there are no caudal appendages, that the teeth of the mandibles are finely pectinated, and that the ovarian tubes run higher up round the sack; in every other respect, there is the closest similarity, even to the arrangement of the bristles on the cirri. In the capitulum, the difference consists chiefly, though not exclusively, in the less development of the valves, and their consequent wide separation: the scuta, however, in Conchoderma, are added to beneath their umbones, or original centres of growth, which is never the case, or only to a very slight degree, in Lepas. Conchoderma has no very close affinity to any other genus. As the majority of authors have ranked the two common species under two distinct genera (Otion and Cineras), I may observe, that there is no good ground for this separation; in the above few specified points in which Conchoderma differs from the genus most closely allied to it, the two species essentially agree together. If we take the nearest varieties of C. virgata and C. aurita, there is but a very slight difference even in the form of their valves, and these hold the same relative positions to each other; the carina, however, is always less developed in C. aurita; even the colouring in both tends to follow the same arrangement. The only obvious distinction between the two species, are the ear-like appendages of C. aurita, which, however, are not developed in its early age, are subject to considerable variation, are of no high functional signification, and are indicated in C. virgata by two prominences on the same exact spots. On these grounds I conclude, that the generic separation of the two species is quite inadmissible.

1. Conchoderma aurita. Pl. III, fig. 4.

Lepas aurita. Linn.[37] Systema Naturæ, 1767.

Otion Cuvieranus (!) Blainvillianus (!) Bellianus (!) Dumerillianus (!) Rissoanus. Leach. Encyclop. Brit., vol. iii, Supp., 1824, and Zoological Journal, vol. ii, p. 208, July 1825.

Otion depressa et SACCUTIFERA. Coates. Journal Acad. Nat. Sci. of Philadelphia, vol. vi, p. 132, 1829.

Otion auritus. Macgillivray. Edinburgh New Phil. Journal, vol. xxxviii, 1845.

Lepas leporina. Poli. Test. utriusq. Sicil., pl. vi, fig. 21, 1795.

Lepas Cornuta. Montagu. Linn. Trans., vol. xi, p. 179, 1815.

Conchoderma auritum et LEPORINUM. Olfers. Magaz. der Gesell. Freunde zu Berlin, 3d Quartel., p. 177, 1814.

Branta aurita. Oken. Lehrbuch der Naturgesch., Th. 11, p. 362, 1815.

Malacotta bivalvis. Schumacher. Essai d’un Nouveau Syst., &c., 1817.

Gymnolepas Cuvierii. De Blainville. Dict. des Sc. Nat., Art. Mollusc., Plate, fig. 1, 1824.

C. capitulo duobus tubularibus quasi-auribus instructo, pone terga rudimentalia (sæpe nulla) positis: scutis bilobatis: carinâ nullâ, aut omnino rudimentali: pedunculo longo, a capitulo distincte separato.

Capitulum with two tubular ear-like appendages, seated behind the rudimentary and often absent terga; scuta bilobed; carina absent, or quite rudimentary; peduncle long, distinctly separated from the capitulum.

Filaments attached to the pedicels of the second cirrus; two upper spines of the maxillæ pectinated.

Hab.—Mundane; extremely common. On ships’ bottoms from all parts of the world. Arctic Sea. Greenland. Pacific Ocean. Often attached to Coronulæ on Whales. On slow-moving fish, according to Dr. A. Gould. Often associated with C. virgata, and Lepas anatifera, L. Hillii, and L. anserifera.

General Appearance.—The capitulum (seen from above in Pl. III, fig. 4 a) is slightly compressed, almost globular, composed of thick membrane, with two large, ear-like, flexible, tubular, folded appendages, at the upper end, opening into the sack. These appendages are seated behind the rudimentary terga when such are present, or behind the spots which they would have held if not aborted. In a young condition they are tubular, but not folded; and often, according to Prof. Macgillivray, either one or both are at first imperforate. They are formed externally of the outer membrane of the capitulum (rendered thin where folded), and internally of a prolongation of the inner tunic of the sack; between the two, there is, as around the whole sack, a double layer of corium. A section across both appendages, near their bases, is given in Pl. III, fig. 4 b, showing how they are folded,—the chief fold being directed from below upwards, with a smaller fold, not always present, from between the two, outwards. The folds sometimes do not exactly correspond on opposite sides of the same individual; they are almost confined to the lower part, the orifice itself being often simply tubular. These appendages are sometimes very nearly as long as the whole capitulum: a section near their bases is sub-triangular. I shall presently make some remarks on their functions and manner of formation.

The Scuta, as well as the other valves, are imperfectly calcified: shape, variable. They usually consist of two lobes or plates, placed at above a right angle to each other, and rarely (fig. 4 c) almost in a straight line; the lower lobe is more pointed and narrower than the upper; the two correspond to the lower and middle lobes in the scuta of C. virgata, the upper one being here absent.

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.

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.

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]

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.

Filamentary Appendages, trophi and cirri all similar to the same parts in C. virgata; but perhaps the anterior faces of the segments in the posterior cirri are rather less protuberant; perhaps also the first cirrus is rather shorter in proportion to the sixth cirrus.

Variety (monstrous).—Amongst the specimens, I found one very young one, in which the scuta had not upper lobes, so that in outline they exactly resembled the scuta in the quite distinct C. aurita: there was not even a rudiment of a carina: the tergum, on one side, was externally bordered by a projecting, semicircular, calcified disc; and the upper points of both terga showed only traces of the rectangular projection, which is the chief characteristic of C. Hunteri. From these traces alone, and from the specimen being mingled with the others, do I here include this variety.

General Remarks.—I have very great doubts whether I have acted rightly in considering this as a species; but as there were many specimens, old and young, all differing remarkably from the common species, this form anyhow deserves description. The points by which it can be distinguished from C. virgata, are—the almost rectangular manner in which the upper portion of the tergum is bent outwards and along the orifice of the sack—the narrowness of all the valves, and especially of the lateral lobes of the scuta,—and lastly, the greater curvature of the carina, which in some specimens runs up far between the terga; had this last character been constant, it would have been an important one, but such is far from being the case. Great as are these differences in the valves, and though common to many specimens, they are not sufficient to convince me that it is a true species, and I should not be at all surprised at varieties, intermediate between it and the common form, being hereafter found;—had a name not been already attached to it, I should not have given one. In the monstrous variety described, we see to what an extent the valves may vary. The C. Hunteri approaches nearest to the var. of C. virgata, called by Leach Cineras chelonophilus, for in both, the top of the capitulum is bluntly pointed and the terga are solid within; in the Var. chelonophilus, the terga and carina are minute, whereas here, though very narrow, they are much elongated. Certainly C. chelonophilus has almost as strong a claim to rank as a species as C. Hunteri; but, in the former, by the aid of other varieties, the differences were almost reduced to the peculiarities in the terga—the valves, the most subject to variation. In C. Hunteri we have other differences, and the form of the terga is even still more peculiar. I have, therefore, provisionally attached to it the specific name by which it is designated in the Museum of the College of Surgeons. From having been long kept in spirits, all aid from colour is lost.

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.

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.