P. capitulo, valvarum duobus, tribus, aut pluribus sub-rostro verticillis instructo: valvis sub-fuscis: lateribus à supremo ad infimum gradatim quoad magnitudinem positis: carinæ margine basali (introrsùm spectanti) ad medium excavato: pedunculi squamarum verticillis densis, symmetricè dispositis.

Capitulum with two, three, or more whorls of valves under the rostrum: valves brownish: latera regularly graduated in size from the uppermost to the lowest: carina with the basal margin, (viewed internally,) hollowed out in the middle: scales of the peduncle symmetrically arranged in close whorls.

Maxillæ with three tufts of fine bristles, separated by larger spines; caudal appendages uniarticulate; filamentary appendages attached to the prosoma.

Capitulum, but little compressed, broad, with the scuta and terga placed in a more oblique direction, with respect to the peduncle, than is usual, so that the line of orifice forms an unusually small angle with the basal margin of the capitulum. The capitulum is composed of several whorls of valves, which gradually decrease in size from above downwards. In a medium-sized specimen there were four whorls under the rostrum; in the lowest of these whorls, there were between eighty and ninety valves, and in the whole capitulum from one hundred and seventy, to one hundred and eighty. The valves in the lower whorls are not of equal sizes. Viewed externally, the valves seem to touch and overlap each other; viewed internally (Pl. VII, fig. 2 a) they are found to be just separated from each other by transparent membrane; none of the valves are articulated together. The outer surfaces of nearly all the valves, except in the two last formed whorls, are much disintegrated, and seem to be composed of alternate white and brown layers of shell. The membrane connecting the valves, as well as that of the peduncle, (in specimens long kept in spirits,) is brown; but in some dried specimens, there are indications of its having been coloured crimson (as in P. cornucopia), round the orifice and between the valves.

Scuta, irregularly oval, convex, narrow at the upper end; basal margin may be almost said to be formed of three short, unequal margins, corresponding with the rostrum, the rostral and the adjoining latus. The edge corresponding with the latter, is the best marked, and is generally slightly hollowed out, as if a piece had been broken off. The tergo-lateral margin is curved and protuberant. The umbo projects a little over the scutal margin of the terga.

Terga, projecting beyond the other valves to an unusually small degree, broadly oval; basal angle bluntly pointed, apex rounded, blunt; scutal margin, hollowed out to receive the upper part of the tergal margin of the scuta; carinal margin curved and protuberant; occludent margin consists of two short sides at right angles to each other. The whole valve in length and area is about equal to the scuta; internally, somewhat concave.

Carina, triangular, rather narrow, internally deeply concave, very slightly curled inwards; basal margin protuberant, with a large central portion considerably hollowed out.

Rostrum, triangular, of nearly the same shape as the carina, but only one third of its length, internally very slightly concave, and with the basal margin various, being either truncated or angularly prominent in the middle.

Latera.—The upper pair (corresponding to the interval between the scuta and terga) is only a trifle larger than the latera immediately beneath; and these only a little larger than those lower down. In the lowest whorl, the valves are very minute, though still about twice as large as the scales on the peduncle, and of a different shape from them. The upper latera (viewed internally) are almost diamond-shaped, owing to the prominence of the basal margin, but this varies considerably in degree. The latera in the next whorl are triangular, with the basal margins protuberant and arched, in a less and less degree in the lower whorls, until in the lowest, the valves are elongated transversely.

Microscopical Structure.—A valve placed in acid leaves a thick opaque mass, formed of three different kinds of tissue, one having a finely shaded appearance; a second with a largely hexagonal reticulated structure, and the third thin, transparent, and marked with arborescent lines, which I imagine to be tubes, as will be hereafter seen in Lithotrya. Near the exterior surface, there are many tubuli. It appears to me probable that the strong tendency which the valves in this species have to disintegrate, is connected with the unusual quantity of animalized tissue contained by them. Externally the valves are covered by a strong membrane, either white or yellow, or white streaked with yellow, and marked by lines of growth, and by longitudinal, sinuous, little ridges.

Peduncle, in the upper part, of rather less diameter than the capitulum; twice or thrice as long as it; tapering a little downwards; surface of attachment wide and flat. Calcareous scales, minute, symmetrically and closely packed together: each scale is much flattened, and its shape, including the imbedded portion, is that of a spear with its point broken off. The basal end of each scale is conically hollow, and from the layers of growth conforming to this hollow, there is a false appearance of an open tube running through the scale.

Attachment.—The surface of attachment is wide: the two cement-ducts, after running down the sides of the peduncle in a sinuous course, within the longitudinal muscles and close outside the ovarian tubes, pass through the corium, and then separately form the most abrupt loops or folds. These are represented in Pl. IX, fig. 2, in which a space about 1/10th of an inch square is given, as seen from the outside. At each of the bends, an aperture has been formed through the membrane of the peduncle, and cement poured forth. The manner in which the discs of cement (b) come out of the two ducts (a a), and reach the external surface, is shown in the section, figure 2 a´. The two tubes are firmly attached to the older layers of membrane, and are covered by the last-formed layers. In a young specimen, the cement-ducts were a little above 2/2000ths of an inch in diameter, which had increased, in a medium-sized specimen, to 5/2000. The cement-glands are retort-shaped, seated near each other, high up in the peduncle.

Size.—The largest specimen which I have seen, was three inches in length including the peduncle; the capitulum was 9/10ths of an inch long, and one in width.

Young Specimen.—I examined one with a capitulum 18/1000ths of an inch long, measured from the lowest whorl to the tips of the terga; the width was only 13/1000ths of an inch; in old specimens the width of the capitulum is greater than the length. The length of one of the scuta was 14/1000ths of an inch, therefore, greater than the width of the entire capitulum, which is not the case with mature specimens. Besides the scuta and terga, the carina and rostrum, and three pair of large latera, there was a lower whorl formed of ten or twelve valves, giving altogether to the capitulum of this very small specimen, either twenty-two or twenty-four valves.

Shape of Body, Sack, Colours, &c.—From the position of the orifice of the capitulum, the animal’s body is suspended to the scuta in a more transverse direction than is usual. The prosoma is well-developed, and is distinctly separated from the three posterior thoracic segments, by a band of thin membrane. The tunic of the basal part of the sack, where it enters the peduncle in a blunt point, is thickened and covered with roughened rounded papillæ. The corium of the sack under the valves, is coloured (after spirits) so dark a brown as to be nearly black; the cirri and trophi are similar, but with a tinge of greenish-purple.

Filamentary Appendages.—Of these there were, on the prosoma of one specimen, twelve pairs, and in another specimen fourteen pairs, seated in two approximate rows; the middle filaments are the longest, equalling about half the diameter of the thorax: each is flattened, and tapers but little towards its summit, which is roughened with microscopical crests serrated on both sides; on the summit, also, there are a few bristles and some very short, thick, minute spines. These appendages are directed rather towards each other, and towards the thorax. I do not doubt that their numbers vary according to the size of the specimen. I believe that they are occupied by testes. Outside these filaments, on each side of the prosoma, there are two very irregular rows of papillæ, intermediate in length between the filaments and the rounded swellings at the bottom of the sack. Beneath the basal articulation of the first cirrus, there is on each side, a short appendage, with a few bristles on its summit. Lastly, on each side of the middle of the mouth, on the prosoma, there is a longer appendage, dark-coloured, furnished with a few scattered bristles on its sides and apex, and directed upwards and a little towards the adductor scutorum muscle.

Mouth.—Labrum highly bullate, but with the uppermost part not more bullate than the lower part, and therefore not overhanging it; basal margin much produced; crest with some small blunt teeth and some bristles. The inner fold of the labrum is much thickened, yellow, punctured, and with a tuft of fine bristles on each side.

Palpi, approaching each other but not touching, club-shaped, or with broad and square extremities, thickly fringed with serrated bristles.

Mandibles with three unusually strong teeth, slightly graduated in size, with the inferior angle very coarsely pectinated; the lower edges of the main teeth are roughened.

Maxillæ, (Pl. X. fig. 13). Spinose edge about half the length of the mandibles; the two upper spines are unusually strong; close under, and almost hidden by them, there is a tuft of fine spines; in the middle there is a second similar tuft mounted on a prominence; and at the inferior angle there is a third tuft, also mounted on a rather wider prominence, not quite accurately figured. In the interspaces between these tufts there are three or four pairs of spines of the usual appearance and projecting just beyond the fine tufts; the upper of the two interspaces is rather narrower, but rather deeper, than the lower interspace. Apodeme very long, irregularly shaped, like an S, with a remarkable elbow near its attachment; apex slightly enlarged, thin and rounded.

Outer Maxillæ.—On the inner margin there is a deep and conspicuous notch, above and beneath which, there is a compact row of serrated bristles; exteriorly the bristles are rather longer.

Olfactory Orifices very prominent, pointing obliquely towards each other.

Cirri.—Posterior cirri moderately long, much curled, with the segments (Pl. X, fig. 27) flattened and wide; the anterior surface hemispherically protuberant, supporting six pairs of spines, of which the lower ones approach each other; between these spines there is a large tuft of very fine spines, of which the central ones are the longest; there is an upper lateral group of very short strong spines; dorsal tufts composed of short, fine numerous spines. First pair seated close to the second pair, short, having in both rami eight segments, whereas in the same individual the second pair, which is nearly twice as long, had thirteen, and the sixth pair eighteen segments. Rami of the first pair nearly equal in length, with their segments, excepting the two upper ones, thickly paved with bristles, in the midst of which a tuft of fine spines, as in the posterior cirri, may be distinguished; the dorsal tufts encircle the whole of each segment; the spine-bearing anterior surfaces are protuberant chiefly in the upper part, so that they are oblique. The posterior (?) ramus has its segments much wider than those on the other ramus; and amongst the common spines, in the third and fourth segments, (counting from the bottom,) there are some very strong spines with their upper ends coarsely and doubly pectinated, each tooth being upwardly bent into a rectangular elbow. In the fifth segment, some of the spines are doubly pectinated with simple teeth; and most of the spines are doubly serrated. The Second (Pl. X, fig. 25) and Third cirri have the five basal segments (5/13ths of the whole number in the second cirrus, and 5/14ths in the third cirrus) of their anterior rami, extremely broad, protuberant, and paved with serrated bristles, amongst which, (except on the actual lowest segment,) there are some simply pectinated spines, and others with their teeth elbowed, exactly as in the first cirrus. The basal segments of the posterior rami of the second and third cirri, differ from the three posterior cirri only in the spines being slightly more numerous; but none of them are pectinated.

Pedicels, rather short; the upper segment resembles, in the arrangement of its spines, the segments of the posterior cirri; the lower segment is longer than the upper, and has two tufts of fine spines, between the two rows of long spines. In the second and third cirri, these two intermediate tufts on the lower segment of the pedicel, are not so distinctly separated from each other.

Caudal Appendages, very small, uniarticulate, blunt and rounded; tips bearing a few, very short, thick spines.

Alimentary Canal.—Œsophagus, somewhat curved at the lower end, where it enters the stomach, which has no cæca; rectum, unusually short, extending from the anus only to the base of the fifth pair of cirri. Within the stomach, from top to bottom, there were thousands of a bivalve entomostracous crustacean.

Generative System.—Both ovaria and testes are largely developed; the former fill the long peduncle; the testes enter both the pedicels of the cirri, and the filamentary appendages on the prosoma; vesiculæ seminales very large, reflected at their ends, extending across each side of the stomach. Penis rather small, coloured purplish, with numerous little tufts of bristles.

Variation.—In some specimens in the British Museum, collected by Sir J. Ross, in the Southern ocean, and in another older set from an unknown source, several parts of the outer tunic of the animal’s body presented the remarkable fact of being calcified, but to a variable degree; whereas in several specimens from California, there was no vestige of this encasement. Considering it most improbable that the calcification of the integuments should be a variable character, I most carefully compared the above-mentioned sets of specimens, valve by valve, trophi by trophi, and cirri by cirri, and found no other difference of any kind; therefore I cannot hesitate to consider both to be the same species. The first Southern specimen which I examined presented the following characters: on the prosoma there was a central longitudinal band, formed of a thin, brittle, brown-coloured calcified layer, which became irregularly rather narrow towards the thorax; on each side it sent out six or seven irregular rectangular plates, which surrounded and supported the bases of the two rows of filamentary appendages; and outside these, some of the papilliform projections also had their bases surrounded by small, calcified, separate rings. The thoracic segments corresponding with the second, fourth, fifth, and sixth cirri had, on each side, an elongated calcified plate; on the ventral surface of the thorax, between the first and second cirri, there were two minute plates. In all the cirri, excepting the first pair, the segments of the rami, and in the three posterior pairs, the segments of the pedicels, had their dorsal surfaces strengthened by oblong, quadrilateral, calcified shields, the upper margins of which are notched for the dorsal tufts of spine, and the two lateral margins are also slightly hollowed out; these are represented in figure 27. The lower segments of the pedicels of some of the cirri, had an additional calcified plate on the antero-lateral face.

These plates are of a faint-brown or yellowish colour, and are conspicuous: the degree of calcification differs considerably; some are quite brittle and very thin, others half horny, and effervesce only slightly in acids. After having been placed in acid, there is no apparent difference between the parts before occupied by the calcified plates and the surrounding membrane; these plates, however, are not superficial, but consist of several of the laminæ, which together compose the ordinary integument, in a calcified condition. Like the integuments of the body, and unlike the valves of the capitulum, these calcified plates are thrown off at each exuviation. Neither the exact shape nor number of the plates corresponded in different individuals, nor even on opposite sides of the same individual. The margins of the plates often have a sinuous corroded appearance; they are, moreover, often penetrated by minute rounded holes, that is, by minute, rounded, non-calcified portions. In one specimen from the Antarctic expedition, there were only here and there a single shield on the segments of the posterior rami, and no plate on the prosoma. Of two specimens in another and older set in the British Museum, from an unknown locality, both had shields on the segments of the cirri, but only one had the large plate on the prosoma. I may here mention that in one specimen, in which the calcified plates were most developed, and which was nearly ready to moult, there were, within the filamentary appendages on the prosoma, small irregular balls of calcareous matter, appearing to me as if calcareous matter had been morbidly excreted, and not like a provision for the future.

Range.—This species, in the present state of our knowledge, seems to range further than any other of the genus, extending from Upper California, (lat. 32° to 35° N.,) across the Pacific, to at least 32° S., perhaps much farther south, for it was collected during the Antarctic expedition, and 32° was the highest latitude traversed by that expedition.

Affinities.—This species is closely related to P. cornucopia and P. elegans, but differs rather more from them, than these two do from each other. In the capitulum the chief distinctive characters are—the more perfect graduation in size, and the greater number, (taking equal-sized specimens,) of the whorls of latera—the darker colours—the central part of the basal margin of the carina in this species, being considerably excised—the peculiar form of the basal margin of the scuta—and lastly, the scutal margin of the terga being more hollowed out. In the animal’s body, the most obvious distinctive character is the uniarticulate caudal appendage. This species agrees with P. elegans, in the presence of the singular elbowed teeth, on some of the spines in the first three pairs of cirri.

4. Pollicipes mitella. Pl. VII, fig. 3.

P. capitulo valvarum unico sub-rostro verticillo instructo: laterum pari superiore (introrsum spectanti) inferiorum magnitudinem ter aut quater superante: lateribus inferioribus utrinque obtegentibus: pedunculi squarmarum verticillis densis, symmetricè dispositis.

Capitulum with only one whorl of valves under the rostrum: the upper pair of latera, viewed internally, are three or four times as large as the lower latera, which overlap each other laterally: scales of the peduncle symmetrically arranged in close whorls.

Maxillæ, deeply notched: caudal appendages, multi-articulated: filamentary appendages, none.

Capitulum, compressed, consisting of the scuta, terga, carina, rostrum, and a large pair of upper latera, with a single lower whorl of smaller valves; these latter vary from 22 in very small specimens, to 26 in large specimens. The capitulum, therefore, is formed of at most 34 valves; but in the largest specimen seen by me, the capitulum being 2.3 of an inch in width, there were only 32 valves. In the smallest, namely, with a capitulum .15 of an inch in width, there were 30 valves. The valves are remarkably strong, and formed of white shelly matter; they are closely approximate, and overlap each other: the scuta and terga are articulated together by a fold; the apices of the valves are either worn and disintegrated, or they project freely like horns beyond the sack, to a much greater extent than in any other recent species of the genus: even a considerable portion of the scuta projects obliquely upwards. The exterior surfaces of the valves (when not worn) are covered by a strong yellow membrane, and the upper free parts are generally attached together for some little length by this same membrane. The valves are plainly marked by the zones of successive growth; and most of them are ribbed and furrowed slightly, from their umbones to their basal margins. The yellow external membrane, examined microscopically, is marked by, or rather formed of, numerous growth-lines, crossed by longitudinal beaded ridges. The tubuli are not numerous, and of small diameter.

Scuta (Pl. VII, fig. 3 a´, a) triangular, with the apex more or less produced, according to the state of its preservation, and a little curved towards the terga; basal margin, and in some degree the tergo-lateral margin, arched, and slightly protuberant; occludent margin thickened, slightly prominent, with the inner edge covered by the yellow membrane, like the exterior surface of the valve. The upper part of the tergo-lateral margin overlaps a little the edge of the tergum, and receives it in a furrow,—the two valves being thus locked together. This furrow lies in the freely-projecting, membrane-covered portion, and extends up to the apex; it is of variable depth. Internally the scuta are concave, and in some old specimens to a high degree. In these latter, the basal margin, towards the tergo-lateral side, is strongly sinuous; the prominences are formed by the terminations of the external longitudinal ridges, and correspond to the interspaces between the valves of the lower whorl. These ridges, which are interesting, from throwing light on similar ridges in some fossil species, are present, both on old and young specimens, and run from the apex of the valve, in a slightly curved line, to the tergo-lateral half of the basal margin, where, as we have just seen, they sometimes form prominences. They consist of three or even four obscure, almost confluent, ridges, of which the middle one is generally (but not always) the smallest: together they cover the whole of that part of the scutum, which is not overlapped along the basal margin by the rostrum and large upper latus; and they seem evidently due to the growth of the shell in this interspace having been freer. So, again, the three or four small, confluent, component ridges have the same relation to the interspaces between the small latera of the lower whorl.

Terga large, four-sided, with the internal growing surface (fig. 3 a´ b), almost diamond-shaped; basal angle blunt, rounded; exteriorly, from the apex to the basal angle there is a rather broad, very slight prominence, which bears the same relation to the carina and upper latus, as do the compound ridges on the scuta to the rostrum and upper latus. The upper part of the scutal margin forms a slightly-projecting, rounded shoulder, though variable in its degree of prominence, in relation to the variable depth of the recipient furrow in the scuta. Externally, parallel to the occludent margin, and close below the prominent shoulder, just mentioned, there is a slight and variable depression, extending up to the apex of the valve. This depression is due to the prominence, variable in degree, of the tergal edge of the recipient furrow in the scuta.

Carina, triangular, strong, inwardly bowed, generally with a large upper portion freely projecting; exteriorly with a narrow, sharp, central ridge or keel, which is solid, the interior concavity not reaching so deep; inner growing surface (fig. 3 b´, b) deeply concave, triangular. Basal margin square—that is, transverse to the longer axis of the carina, or it even rises (as is best seen in the growth-ridges) a little towards the exterior keel. On each side of the central exterior keel, there is a narrow longitudinal ridge, corresponding with the interspace between the sub-carina and the next-but-one latus of the lower whorl; the latus next to the sub-carina is very small, and overlies the ridge itself. In a very large specimen, these lateral longitudinal ridges formed (as they likewise did on the rostrum) slight prominences on the basal margin. In one specimen the carina was straight.

Rostrum closely similar, in almost every respect, to the carina, even to the exterior, lateral, longitudinal ridges, and in their relation to the interspaces in the lower whorl. The valve is generally not so long, but rather wider, more inwardly bowed, and with the exterior solid keel less prominent than in the carina. The inner growing surface (fig. 3 b´ d) is less acuminated at its upper end.

Upper pair of Latera.—These are much larger than the remaining valves of the lower whorl; they are straight, triangular, and much acuminated, with their apices, when well preserved, extending far up, for fully three fourths of the height of the scuta. They nearly equal in length the carina. The growing surface (fig. 3 b´, a) is flat, triangular, in well-preserved specimens forming only a third or a quarter of the entire length of the valve. In the middle of the basal margin there is a very slight prominence, corresponding with a slight external central ridge, formed as heretofore by the overlapping of two of the valves of the lower whorl. Basal margin nearly on a level with that of the scuta and with the basal points of the terga. The foregoing eight larger valves form the main cavity, in which the body of the animal is lodged.

Valves of the Lower Whorl.—These, seen externally, seem to belong to more than one whorl, but internally their basal margins stand on a level. They vary in number, as already stated, from 22 to 26. I have seen an individual with a valve more on one side than on the other. They are of unequal sizes, but they are rather variable in this respect: the largest are not above half the size of the upper latera: three or four pairs, together with the sub-rostrum (e) and sub-carina (c), are always larger than the others: these two latter valves differ from the others only in being more concave. Seen externally, all these valves project considerably, and curl a little inwards, with their apices generally worn and truncated. Viewed internally (fig. 3 b´), whilst the valves are in their proper places, the inner and growing surfaces of the smallest are seen to be triangular,—of the larger, some are rhomboidal, and others quadrilateral with the upper side much longer than the lower. These latter valves overlap the upper parts of the little valves on both sides of them; the rhomboidal valves overlap a valve on one side, and are overlapped on the other; the triangular valves are overlapped on both sides.

The corium lining the capitulum is produced into narrow purple crests, which enter the interstices between the valves, more especially along the line separating the upper and lower whorls. There is, also, a distinct flattened, tapering, free projection of corium, which enters between the carina and sub-carina; and another between the rostrum and sub-rostrum.

Peduncle, much compressed, short, rarely as long as the capitulum; in one very large specimen it was extremely short, barely one fifth of the length of the capitulum. The attached portion, which is moderately pointed in young specimens, becomes extremely broad in old specimens. The calcified scales sometimes differ a little in size, in specimens of the same age: they are always compactly and symmetrically arranged: in old specimens they are much larger than in young ones: each scale has, at first, a transversely elliptic growing base, which ultimately becomes nearly circular. Exteriorly the tips of the scales are always disintegrated; they are sometimes club-shaped, owing to the scales having been re-added to after a period of reduced growth. The scales are fringed with brown disintegrating membrane.

Attachment.—At the base of the peduncle, the two cement-ducts running together, twist about in a singular manner, and at their bends pour forth cement. According to the age of the specimen, the ducts vary in diameter from 1/2000th to 5/2000ths of an inch. The two cement glands are small and difficult to find; they are retort-shaped, with two ovarian tubes entering each. They lie close together, in nearly the centre of the peduncle, and less than half-way down it. This proximity of the two cement-glands, and their position low down the peduncle, are of interest in relation to the position of these same glands in the sessile Cirripedes.

Size and Colours.—This is the largest and most massive species in the family. I have seen one specimen in the British Museum, from the Coast of China, 2.3 inches across the capitulum, and 1.5 in length, with the valves surprisingly thick. The relative width and length of the capitulum varies. The sack (in specimens long kept in spirits) is dirty purple, and exteriorly between the scuta, dark purple. The cirri, trophi, penis, caudal appendages, three posterior segments of the thorax, and the abdominal surface are dark-brownish purple.

Body.—Thorax remarkably compressed and carinated; prosoma pretty well developed. Extending from the base of the second cirrus, to nearly a central line on the thorax, there is on each side a rounded ridge: there is a second transverse ridge, running from the base of the first cirrus to near the adductor scutorum muscle: these ridges seem formed merely to allow of the larger development of the testes.

Mouth.—Labrum highly bullate; crest without any teeth, but with a few minute hairs. The inner fold of the labrum forming the supra-œsophageal cavity, is thickened, and shows a trace of a central line of junction, as in Sessile Cirripedes.

Palpi (Pl. X, fig. 7), small; of a singular club-like shape, owing to the convexity of the outer margin; exterior spines long, all doubly serrated.

Mandibles (Pl. X. fig. 1), with five teeth, of which the second is very small; inferior angle coarsely pectinated.

Maxillæ (fig. 14), with a deep narrow notch (bearing some fine spines) beneath the two upper great spines, which stand on a prominence; edge straight, bearing fourteen or fifteen pairs of spines: on the inferior angle there is an obscure tuft of shorter and finer spines: apodeme long, sinuous, and slender.

Outer Maxillæ (fig. 17), with the inner margin divided by a deep notch into two lobes, of which the upper one is rather short; both are clothed with a compact row of short bristles; exterior margin with longer bristles.

Olfactory Orifices, large and prominent to an unusual degree.

Cirri, moderately long and curled; the four posterior pair are alike; each segment has its anterior face somewhat protuberant, and bears six pairs of long spines, with a rather large, narrow tuft of intermediate spines, some of which are finely and doubly serrated. The dorsal tufts consist of short, thick spines, with some fine longer ones. The first cirrus is seated near the second; its rami are slightly unequal in length; lower segments paved with bristles; one ramus is thicker than the other, and some of its segments have coarsely pectinated spines. Second cirrus has the five basal segments of its anterior ramus highly protuberant, and paved with bristles, of which some are coarsely pectinated; the basal segments of the posterior ramus are rather more thickly clothed with bristles than are the posterior cirri, but otherwise resemble them. The third cirrus, as already stated, is exactly like the three posterior pairs; and this is a very unusual circumstance. On the dorsal surfaces and sides of the pedicels of the posterior cirri, there are some scattered, short, thick, minute spines.

Caudal Appendages, multi-articulate: in a medium-sized specimen, each contained eight segments, which reached half-way up the upper segment of the pedicel of the sixth cirrus. Lower segments flattened; the upper, tapering, and cylindrical; all have their upper margins furnished with stiff, little spines. In a young specimen (only .3 of an inch in length, including the peduncle), the caudal appendage contained only four segments, and the tip did not reach to the upper edge of the lower segment of the pedicel of the sixth cirrus.

Stomach, without cæca.

Generative System.—Vesiculæ seminales not reflexed at their broad ends; white, spotted with black. Testes, pear-shaped, borne on long footstalks: penis covered with minute bristles, in little tufts arranged in straight lines. The ovarian tubes fill up the peduncle to its base, but do not surround the sack; they are of small diameter, and simply branched. There is a very narrow ovigerous frænum, with a straight edge, lying on each side under the line of junction between the scutum and upper latus.

Affinities.—This species differs from all the others of the genus, in the third cirrus resembling exactly the three posterior pairs. In most of its characters—namely, in the symmetrical arrangement of the scales on the peduncle, in the considerable size of the valves of the lower whorl, in the general approximation of the valves, in the multi-articulated caudal appendages, in the form of the outer maxillæ, in the prominent olfactory orifices, in the basal segments of the anterior ramus alone of the second cirrus being paved with bristles, there is more affinity to P. cornucopia, P. elegans, and P. polymerus than to P. sertus and P. spinosus.

In the scuta and terga being articulated together, in the union of all the valves by stiff membrane, in the peculiar manner in which the valves of the lower whorl overlap each other, in the corium entering between some of the valves in filiformed appendages, in the near equality of size of the rostrum and carina, in the shortness of the peduncle in old specimens, in the position of the cement-glands, and lastly in the characters of the third pair of cirri, this species presents a closer affinity to the sessile Cirripedes, more especially to the Chthamalinæ, than does any other species of any other genus amongst the Lepadidæ. The movements, however, of the four opercular valves are not at all more independent of the other valves, than in the other Pedunculated Cirripedes; and the peduncle is furnished with all its characteristic muscles.

5. Pollicipes spinosus. Pl. VII, fig. 4.

P. capitulo valvarum uno aut pluribus sub-rostro verticillis instructo: laterum pari superiore vix inferioribus longiore: membranâ valvas tegente (post desiccationem) subfuscâ flavescente: pedunculi squamis inæqualibus, non symmetricis: verticillis longiusculè distantibus.

Capitulum with one or more whorls of valves under the rostrum: upper pair of latera only slightly larger than the lower latera: membrane covering the valves (when dried) light yellowish-brown: scales of the peduncle of unequal sizes, unsymmetrical, arranged in rather distant whorls.

Maxillæ, with the edge square and straight: caudal appendages uniarticulate: filamentary appendages, none.

Capitulum, flattened, triangular, broad, with the valves varying in number, in full-grown specimens of the same size, from 30 to above 60; the scuta, terga, and carina are very much larger than the other valves; the rostrum, however, is nearly half the size of the carina; the remaining valves are exceedingly small. In some specimens there is only one whorl under the carina; in other specimens there are distinctly two whorls. The scuta, terga, and carina stand pretty close together; they are moderately thick, and are covered, in chief part, by yellowish-brown membrane, which is destitute of spines.

Scuta, triangular, broad, basal margin slightly protuberant.

Terga, as large as the scuta, flat, regularly oval, basal point blunt and rounded.

Carina very slightly curved, triangular, internally rather deeply concave, basal margin straight. The inner and growing surface is four fifths of the entire length of the valve. In half-grown specimens the apex projects a little outwards.

Rostrum, small, much curled inwards; the basal margin is much hollowed out; the inner surface is broadly triangular, more than twice as wide as high, and about one fourth of the entire length of the valve. The remaining valves, about 26 in number, do not correspond on the opposite sides of the same individual, they are exceedingly small, with the sub-carina, sub-rostrum, and three pairs of latera a trifle larger than the lower latera, which are generally arranged in two whorls. In shape all the latera are nearly alike; they consist of flattened styles, with their inner surfaces transversely oval, and more or less elongated, the larger ones being most elongated.

Peduncle, broad, barely as long as the capitulum. The calcareous scales are irregularly shaped, minute, elongated and pointed, placed in separate transverse rows, and crowded together in each row. Only the scales in the uppermost row grow regularly; but some of the lower scales continue to be added to irregularly, and hence are the largest. On the other hand, the lower part of the peduncle, from the first formed scales having been worn away, is often quite naked. From this cause, and from the continued and irregular growth of some of the lower scales, the rows in this part of the peduncle, generally become irregular. The surface of attachment is broad.

In a half-grown specimen, with a capitulum only 3/10ths of an inch long, all the lower valves were considerably larger in proportion to the scuta, terga, and carina, than in full-grown individuals.

Size and Colours.—Length of capitulum in the largest specimen, 7/10ths of an inch; breadth, slightly exceeding the length. Colours after having been long in spirits—upper part of sack, thorax, pedicels of cirri, and penis, clouded with fine purple; cirri banded with the same; exterior convex surface of the outer and inner maxillæ and palpi dark purple; prosoma yellow. The membrane of the peduncle and of the capitulum is dirty yellow, with bands of purple between some of the valves.

Filamentary Appendages, none. Ovigerous fræna placed near the middle of the basal margin of the scuta; small, semi-oval, with an elliptical ring of bead-like glands; glands seated on long footstalks.

Mouth.—Labrum far produced towards the adductor muscle; upper part highly bullate, nearly equalling the longitudinal diameter of the rest of the mouth, and very slightly overhanging the lower part; crest with very minute bead-like teeth.

Palpi, with their inner margins considerably excised, most thickly clothed with spines.

Mandibles, with three strong teeth, two unequal-sized small teeth being placed between the first and second, thus making five altogether; inferior angle broad, pectinated.

Maxillæ, with its edge broad, straight, bearing about twenty pairs of spines, shorter than the large upper spines.

Outer Maxillæ, with the bristles in front, continuous, and without any notch; exterior surface with a prominence clothed with long spines. Olfactory orifices slightly prominent.

Cirri.—First cirrus placed near to the second; posterior cirri not much elongated, with their segments slightly protuberant, bearing four pairs of spines, of which the lower pair is small; spines slightly serrated. In the lower segments, these spines are exceedingly unequal in length, the inner spines on both rami, not being above one fourth of the length of the outer corresponding spine in each pair. The tufts intermediate between these pairs, are not very large: on the lateral upper rims there are some strong, short spines: dorsal tufts with short, thick spines. First cirrus about three fourths as long as the second cirrus, with numerous tapering segments, three or four of the lower ones being thick and protuberant: in the first cirrus there are eleven segments, and in the sixth cirrus, seventeen. Second cirrus, with the anterior ramus slightly thicker than the posterior ramus: a few of the basal segments of both rami are protuberant, and thickly clothed with spines. In the third cirrus, the two rami are nearly equally thick, with some of the basal segments in both clothed, like a brush, with spines. In these brushes on the first, second, and third cirri, most of the spines are doubly toothed, each tooth being simply conical.

Caudal Appendages, small, much flattened, straight on the exterior side, and curved on the inner side, with a row of short, rather thick spines on the crest, and a few on the exterior margin.

The Affinities of this species will be given under the head of the following, P. sertus.

6. Pollicipes sertus. Pl. VII, fig. 5.

P. capitulo valvarum uno aut pluribus sub-rostro verticillis instructo: laterum pari superiore vix inferioribus longiore: membranâ valvas tegente (post desiccationem) fusco rufescente obscuro: rostro dimidiam carinæ longitudinem æquante, superficiei internæ altitudine latitudinem plus duplo superante: pedunculi squamis inæqualibus, non symmetricis: verticillis longiusculè distantibus.

Capitulum with one or more whorls of valves under the rostrum: upper pair of latera only slightly larger than the lower latera: membrane covering the valves (when dried) dark reddish-brown: rostrum half as long as the carina, with its inner surface more than twice as high as broad: scales of peduncle of unequal sizes, unsymmetrically arranged in rather distant whorls.

Maxillæ with two tufts of fine bristles, separated by larger spines: caudal appendages uniarticulate: filamentary appendages none.