5. Conchoderma

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_ 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] [34] The general title to the volume, containing four Quarterly parts, is dated 1818; but as in the 'Journal de Physique,' for July, 1817, the editor refers to Conchoderma, the Quarterly Part containing this genus must have appeared before 1818: Lamarck gives the year 1814 as the date of the paper in question, and I have accordingly followed him. From a similar reference by the editor, it appears that Schumacher's volume appeared before the number of the 'Journal de Physique' containing Leach's Paper. [35] Under these nine generic names, the two common species of Conchoderma have received thirty-three different specific denominations, caused partly by changes of nomenclature, and partly from varieties having ranked as species.

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-oesophageal 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-oesophageal 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.

[36] Remarks on the Cirripedia, &c.; 'Edin. New Phil. Journal,' vol. xxxix, p. 171.

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. [37] Many authors (Poli, Montagu, &c.,) have doubted from the strangely mistaken description, viz., "ore octovalvi dentato," whether this species could be the Lepas aurita of Linnæus. But in the Linnean Society, there is a proof plate from Ellis's "Account of several rare Species of Barnacles," in 'Phil. Trans.,' 1758, with an excellent figure of the C. aurita, and on the margin in Linnæus's handwriting is the name Lepas aurita.

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. [38] See page 136 respecting this date.

C. Scutis trilobatis: tergis intùs concavis, apicibus introrsùm leviter curvatis: carinâ modicâ, leviter curvatâ: pedunculo in capitulum coalescente. Scuta three-lobed: terga concave internally, with their apices slightly curved inwards: carina moderately developed, slightly curved: peduncle blending into the capitulum. No filament attached to the pedicel of the second cirrus. Var. chelonophilus (Pl. III, fig. 2 c). Terga, minute, nearly straight, solid, acuminated at both ends, placed far distant from the other valves: carina, either minute and acuminated at both ends, or moderately developed and slightly arched and blunt at both ends: lateral lobes of the scuta broad: valves imperfectly calcified.

Hab.--Mundane: extremely common on ships' bottoms from all parts of the world. Falkland Islands. Galapagos Islands, Pacific Ocean. Attached to sea-weed, turtle and other objects. Often associated with Conchoderma aurita, Lepas anatifera, L. Hillii, and L. anserifera.

General Appearance. Capitulum, flattened, gradually blending into the peduncle; summit square, rarely obtusely pointed. Membrane, thin. Valves, thin, small, sometimes imperfectly calcified, very variable in shape and in proportional length, and therefore, situated at variable distances from each other, but always remote and imbedded in membrane. Scuta, trilobed, consisting of an upper and lower lobe (the latter generally the broadest), united into a straight flat disc, with a third lobe standing out from the middle of the exterior margin, generally at an angle of from 50° to 70° (rarely at right angles) to the upper part, and generally (but not always) bending a little inwards. The shape of the lateral lobe varies from rounded oblong to an equilateral triangle; as it approaches this latter form, it becomes much wider than the upper or lower lobes. In one specimen, and only on one side, the scutum (fig. 2 d) presented five points or projections. In some specimens, the scuta are very imperfectly calcified, and consist of several quite separate beads of calcareous matter of irregular shape, held together by tough brown membrane. Terga, extremely variable in shape, placed at nearly right angles to the scuta: beyond their carinal ends (fig. 2 b), the capitulum presents two small prominences, which are important as indicating the position of the homologous, ear-like appendages in C. aurita.[39] The upper ends of the terga are imbedded in membrane, and project freely like little horns for about one third of their length: this free portion exactly answers to the projecting portion, bounded by the two occludent margins, in the terga of Lepas. The freely projecting portion is generally curled inwards, and the carinal portion more or less outwards,--the form of the letter =S= being thus approached; but the curvatures are not exactly in the same plane. The whole valve is generally of nearly equal width throughout, the carinal part being a very little (but in some specimens considerably) wider; internally, it is deeply concave; both points generally are blunt and rounded. In some rare varieties (Cineras chelonophilus of Leach, fig. 2 c), the terga are much smaller and flat, with both points sharp, the whole upper portion being much and abruptly attenuated, and internally, without a trace of a concavity. Generally, the terga are about two thirds of the length of the scuta, rarely only half their length; generally, they are separated from the apices of the scuta by about their own length, rarely by twice their own length. Generally, the terga are shorter than the carina, but sometimes a very little longer than it: generally they are distant by one third or one fourth of their own length from the apex of the carina, rarely by their entire length.

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

Carina (fig. 2 a), lying nearly parallel to the scuta, concave within, very slightly bowed, of nearly the same width throughout, but with the lower third beneath the umbo, generally a trace wider than the upper part. Length, variable, generally rather longer (sometimes by even one third of its own length) than the scuta, but sometimes equalling only three fourths of the length of the scuta; generally longer than the terga. Upper and lower points rounded; in rare varieties, both ends are sharply acuminated. The carina and terga are generally most acuminated where they are smallest and least perfectly calcified; and consequently, in this same state, the valves stand furthest apart. Peduncle, flattened, gradually widening as it joins the capitulum, to which it is generally about equal in length, or a little longer. Filamentary Appendages.--Six on each side (Pl. IX, fig. 4), of which one (h) is seated on the posterior margin of a swelling, beneath the basal articulation of the first cirrus, and this is the longest; the second (g) is short and thick, and is seated a little lower on the side of the prosoma, (near to this, there are also two little pap-like eminences;) the third (i) is seated on the posterior margin of the pedicel of the first cirrus, above the basal articulation; the fourth, fifth, and sixth (j, k, l) in similar positions on the pedicels of the third, fourth, and fifth cirri. These three latter filaments are shorter and smaller than the first three. At the base of the second cirrus, which has no proper filament, there is a swelling as if one had been united to it. Mouth.--Mandibles, with the basal edges of the five teeth pectinated by minute, short, strong spines on one side; inferior angle extremely short. In one specimen, there was a minute pectinated tooth between the first and second; in another, the second tooth was bifid on its summit; in another, the fourth was rudimentary. Maxillæ, with five steps: sometimes each step commences with a spine rather larger than the others; at the upper angle, there are two large unequal spines (neither pectinated,) with a third longer and thinner, seated a little below. Outer maxillæ (Pl. X, fig. 16), simple. Cirri, with twice as many segments in the sixth cirrus as in first; spines on the first and second cirri doubly serrated. Colours (when alive).--Capitulum and peduncle grey, with a tinge of blue, with six black bands, tinged with purplish brown. The two bands near the carina become confluent on the peduncle, and sometimes disappear; the carina is edged, and the interspace between the two scuta, coloured with the same dark tint. The whole body and the pedicels of the cirri are dark lead-colour, with the segments of the cirri almost black: in some specimens, the colour seems laterally abraded from the cirri. Ova white, becoming in spirits pinkish, and then yellow. The dark bands on the capitulum and peduncle become in spirits purple; but are sometimes discharged; the general grey tint disappears. Professor Macgillivray states that many individuals are light-brown or yellowish-grey, with irregular brown streaks, or crowded dots: he states that in very young specimens the colours are paler, and the valves spicular. Size.--The largest specimen which I have seen, had a capitulum rather above one inch long and three fourths of an inch wide: growth very rapid. Monstrous Variety.--In the British Museum, there is a dried and somewhat injured specimen of a monstrous variety, the Pamina trilineata of J. E. Gray: it differs from the common form only in having a tubular projection, just behind the notch separating the upper points of the terga; this tube springs from over the terga, and is, therefore, in a different position from the ear-like appendages in Conchoderma aurita. It does not open into the sack: the membrane composing it appears to have been double in the upper part, and to have been lined with corium: in short, this tube seems to have been an excrescence or tumour, of a cup or tubular form. General Remarks.--It will have been seen how much subject to variation the valves of this species are. When I first examined the Cineras chelonophilus of Leach, from 36° N. lat., Atlantic Ocean, and found in many specimens, both old and young, that the terga were very small, flat, acuminated at both ends, with a projecting shoulder on the carinal margin, and situated at about their own length from the apex of the carina, and at twice their own length from the scuta; and when I found the carina acuminated at both ends, and the scuta very imperfectly calcified, with the lateral lobe broad, flat, and standing out at right angles; and lastly, when I found the whole capitulum bluntly pointed, instead of being square on the summit, I had not the least doubt, that it was a quite distinct species. Afterwards, I found in the Cineras Olfersii of Leach, from the South Atlantic, the same form of terga; but within slightly more concave or furrowed, and not nearly so small, and therefore not placed at above half so great a distance from the other valves; and here, the carina had its usual outline, as had nearly the scutum on one side, whereas, on the other side, it presented a new and peculiar form, having five ridges or points, and was imperfectly calcified; seeing this, it was impossible to place much weight in the precise form or size (and therefore, relative separation,) of the calcified valves; and on close examination, I found every part of the mouth and cirri identical in Leach's Cineras chelonophilus and C. Olfersii, and in the common form. Therefore, I conclude, that C. chelonophilus, and still more C. Olfersii, are only varieties; the terga presenting the greatest, yet variable, amount of difference, namely, in their acumination and flatness. We know, also, that in the species of the closely allied genus of Lepas, the terga are very variable in shape, and this is the case, even in a still more marked degree, in Conchoderma aurita. Professor Macgillivray, I may add, has come to a similar conclusion regarding the extreme variability of the valves of this species. As the varieties here mentioned are very remarkable, and may perhaps turn out to be true species, I think they are worth describing in some detail: I will only further add, that we must either make several new species, or consider, as I have done, several forms as mere varieties. C. VIRGATA, var. CHELONOPHILUS of Leach. Pl. III, fig. 2 c.

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

Capitulum not above half an inch long, composed of very thin membrane, with six bands (as stated by Leach) of faint colour; summit bluntly pointed; valves very small, far distant from each other; the scuta are imperfectly calcified, the central part of the umbo consisting of thick, brown chitine, with imbedded shelly beads; terga and carina perfectly calcified. Scuta trilobed, flat, within slightly concave, upper lobe rather more acuminated than the lower; lateral lobe triangular in outline, twice as wide as either the upper or lower lobes; lying in the same plane with them and standing out at almost exactly right angle. Terga, flat; placed obliquely to the scuta, and barely half as long; separated from them by nearly twice their own length; upper and lower points acuminated; the umbo on the carinal margin forms a projecting shoulder; the scutal margin is straight, they are separated by nearly their own length from the apex of the carina. Carina narrow, very slightly arched, within slightly concave, both points acuminated; lower third rather wider than the upper part; in length equalling three fourths of the scuta, and longer by one third than the terga; about as wide as the latter. Filaments, Cirri, and Mouth exactly as before. In some specimens sent to me by the Rev. R. T. Lowe from off the Testudo caretta, taken near Madeira, the scuta have their lateral lobes broad and nearly rectangular: the carina extends nearly to between the terga: the terga are nearly straight, somewhat pointed at both ends, distant from the scuta, almost solid within, with their upper points bowed outwards: the whole capitulum is bluntly pointed, as in the var. chenophilus, to which form this makes a rather near approach. C. VIRGATA, var. OLFERSII. CINERAS OLFERSII. Leach. Tuckey's Congo Expedition.

Hab. South Atlantic Ocean.

Scuta, unlike on the opposite sides of the same individual, on one side with a single lateral lobe as usual, but this very narrow, on the other (fig. 2 d), with five lobes or projections. Terga slightly concave within, separated by a little more than their own length from the tips of the scuta, and by one third of their own length from the tip of the carina. Carina longer than the scuta by about one fifth or one sixth of its own length, blunt at both ends, considerably bowed. Again, I possess a group of remarkably fine specimens given me by Mr. L. Reeve, from the southern ocean, (as I infer from a young Lepas australis adhering to them,) in which all the individuals, young and old, are characterised as follows:--Scuta, with the lateral lobe generally broad, but to a very varying extent, with the upper and lower lobes extremely sharp. Terga separated from the scuta, by one and a fourth of their own length, and by their own length from the carina; somewhat acuminated at both ends, nearly straight, with a very slight shoulder near the umbo. Carina equalling the terga in length, and about three fourths of the length of the scuta; neither the upper nor lower point much acuminated. All the valves most imperfectly calcified: in one specimen, the scutum on one side was simply horny, without a particle of calcareous matter. The summit of the capitulum nearly intermediate in outline between the common square, and bluntly-pointed form of var. chelonophilus. I compared the cirri and trophi with those of a common variety, and could detect not the smallest difference. This variety differs from var. Olfersii, in the less development of its carina, and from chelonophilus, in the greater development of its carina, and especially of its terga. It would appear as if the great variability of the valves was connected with the absence of calcareous matter. 3. CONCHODERMA HUNTERI. Pl. III, fig. 3.

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

C. valvis angustis: scutis trilobatis, prominentiâ laterali non latiore quam inferior: tergorum parte superiore pæne rectangulè secundùm aperturæ marginem flexâ: carinâ valde arcuatâ: pedunculo brevi, in capitulum coalescente. Valves, narrow: scuta, trilobed, with the lateral lobe not wider than the lower one: terga, with the upper part bent almost rectangularly along the margin of the orifice: carina considerably arched: peduncle short, blending into the capitulum. No filament attached to the pedicel of the second cirrus. Var.--Carina absent; scuta, with the upper lobe absent; terga, with the rectangular projection little developed.

Attached to the skin of a snake, probably the Hydeus or Pelamis bicolor, and therefore from the tropical Indian or Pacific Oceans. Mus. Coll. of Surgeons.[40] [40] I owe to the kindness of Professor Owen, an examination of these specimens, and information regarding them.

Capitulum, with the membrane very thin; summit obtusely pointed. Valves linear and thin. Scuta, elongated, flat, with the upper projecting lobe rather more acuminated than the lower, and equalling it in length; lateral lobe not wider than the lower, and about as long as it, forming an angle of about 55° with the upper one. Terga, of somewhat variable length, generally about half as long as the carina, narrow, and of nearly equal width throughout; lower point sharp; externally convex; internally solid, with a trace of a central depressed line; the upper fourth part generally a little bowed out of the plane of the lower part, and abruptly bent at rather above a right angle along the occludent margin of the orifice. These valves are situated at about half their own length from the upper points of the scuta. Carina considerably arched, extending to the lower points of the terga, or running up between them for even half their length; equally narrow throughout; scarcely broader than the terga; both points rounded; internally concave; the lower point does not extend as far down as that of the lower lobe of the scuta. Peduncle, narrow, shorter than the capitulum, which, in the largest specimen was 4/10ths of an inch long. Longitudinal purple bands appear to have originally existed on the peduncle. 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. _

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