CHTHAMALUS. Ranzani. Memoire di Storia Naturale, 1820.
EURAPHIA. Conrad. Journal Acad. Nat. Sc. Philadelphia, vol. 7, 1834.
Compartments six: basis membranous, but sometimes in appearance calcareous, owing to the inflected parietes.
Distribution mundane; attached generally to littoral rocks and shells.
This, the typical genus, is the largest and widest distributed group of the sub-family Chthamalinæ. The founder of the genus apparently did not perceive its essential character; Savigny, however, as is evident from the excellent figure in the great work on Ægypt, perfectly understood the difference between Chthamalus and Balanus. I was first indebted to Dr. J. E. Gray for explaining to me this difference; but the only published account which I have met with is in a paper by the Rev. R. T. Lowe,[130] in which he states, on the authority of Mr. Clark of Bath, that in Chthamalus the anterior compartment or rostrum has alæ like the posterior compartment or carina, the anterior or rostro-lateral compartments being destitute of alæ. These characters being exactly reversed in Balanus, as I have already explained (p. 176) under the sub-family of Balaninæ.
[130] ‘Zoological Journal,’ vol. 3, p. 76, 1828.
The shell, owing apparently to its containing much animal matter, is particularly subject to disintegration; and when thus much affected it is quite impossible to distinguish the species by external characters. It is, in fact, best to cast on one side external appearance, though when the shells happen to be well preserved, each species has its own peculiar aspect. We have in this genus smooth and plicated, cylindrical and depressed varieties of most of the species. The development of the radii is very apt to vary, and even the compartments often become so completely united and calcified together that the sutures are almost or quite obliterated. A more serious difficulty in discriminating the species, arises from the fact of the opercular valves, not only varying extremely in external appearance in consequence of the greater or less disintegration of their apices, and consequent exposure of their articular ridges and furrows (compare fig. 1 a, 1 b, 1 c, in Pl. 18), but from their truly varying in outline with the varying shape of the shell: this latter circumstance is probably due to the opercular membrane which unites the valves to the shell being very narrow, and in consequence, differences in the shape of the shell affect the opercular valves, in a manner and to a degree to which the Balaninæ are not subject (compare fig. 1 e, 1 f, 1 h, in Pl. 18). The scuta, on the other hand, differ to an unusually slight degree in the different species. In the common Chthamalus stellatus, which abounds on the southern British shores, the whole external aspect of the shell is often so completely masked, owing to its varying shape, its obliterated sutures, its deeply disintegrated and punctured surface, and by the corroded condition of its opercular valves, that I have found this species, in the collections of naturalists who have attended to cirripedes, arranged actually on the same tablet, mingled with specimens of Balanus balanoides. I have myself several times found it less troublesome to discriminate these two genera by the included animal’s body than by the shell,[131] though the latter, when well preserved and developed, possesses such obviously well-marked characters: the same thing has occurred to me with some of the other species.
[131] It will be found ultimately to save time and trouble, to soak for half an hour in hot caustic potash, a specimen out of each group of shells to be examined, and then well wash and brush the separated valves and compartments; this process has been followed by me with all the species here to be described.
General Appearance.—The shell is generally depressed, but sometimes, when growing in groups, cylindrical. The surface is either smooth or longitudinally folded; and, as already stated, very apt to be deeply disintegrated. The radii, when developed, are narrow, with their summits oblique and rounded; but they are often quite absent, and sometimes even the sutures are almost obliterated. The rostrum and carina are of the same shape and size, and the two lateral compartments on each side are of nearly equal breadths. The orifice is generally sub-rhomboidal, being widest towards the carinal, instead of towards the rostral end, as is usual in Balanus: but in Chthamalus fissus the orifice is narrow and elongated. The opercular valves have their apices generally disintegrated and worn away, and are then seen to be deeply locked together. The colour of the shell is dirty white or dull purplish-red or brown; but in C. intertextus rich violet-purple. The species are small, not often exceeding half an inch in basal diameter, with the exception of C. Hembeli, of which I have seen a specimen two and three quarters of an inch in diameter.
Scuta.—These present no particular character, excepting in most cases the large development of the articular ridge, and sometimes the presence of a furrow above the articular ridge, of which only traces can rarely be detected in Balanus; hence in these cases, as in C. Hembeli (Pl. 18, fig. 5 a, 5 c) and scabrosus (Pl. 19, fig. 2 a, 2 c), the line of articulation between the scutum and tergum is more complicated than is usual. There is generally a slight pit, sometimes even furnished with small crests, for the lateral scutal depressor muscle: in C. scabrosus (fig. 2 d, q) a part of this muscle is attached to a small pit at the basi-scutal corner of the tergum,—a fact of which I have observed no instance in any other genus. In C. intertextus the terga and scuta are calcified together, without even a suture being visible on their internal faces. In C. Hembeli the valve is externally marked by a few longitudinal furrows.
The Terga, like the scuta, have a prominent articular ridge and deep furrow. In many specimens of C. stellatus and in C. scabrosus the valve is narrow: in C. fissus it is triangular and nearly equilateral. The crests for the depressores muscles are well developed: in C. scabrosus (Pl. 19, fig. 2 d, p) these crests are united into a plate, which, together with the outer lamina of the valve, forms a deep narrow pit: in C. Hembeli the crests are furnished with small sub-crests. The opercular membrane is narrow; it is sometimes furnished with a few minute spines.
Structure of Parietes.—The parietes are solid, and composed of successive layers of shell; the inner surface varies in condition in the same species, being either smooth or marked with branching impressed lines, or mamillated, or often irregularly punctured for the entrance of tubuli. Owing to these tubuli, the walls, when externally disintegrated, often become punctured. In certain depressed varieties of both C. stellatus and scabrosus the walls are supported by irregular depending columns, placed along either one side or both sides of the sutures. In C. intertextus we have the remarkable character of the wall of the shell growing (I presume after a certain age) almost rectangularly inwards, thus forming a rather wide, flat, calcareous rim round the central basal membrane. In C. Hembeli the internal basal edges of the parietes, in one moderately young specimen, were rugged with irregular points, but presented no other remarkable appearance; but in five old and very large specimens, the whole basis was calcareous, being absolutely continuous with the inner lamina of the parietes, showing that the latter had grown flatly inwards all round, and had then become confluent in the middle, so that there was no longer any basal membrane; excepting, no doubt, that which had existed in the younger stage, and which would be preserved in a functionless condition between the surface of attachment and the inflected parietes.
When an opercular valve or compartment is dissolved in acid, layers of tissue are left, and these are seen to be penetrated by tubuli, which enter at the punctures before mentioned on the inside of the shell: these tubuli often stand in groups of three or four together; they are about 1/10000th of an inch in diameter. Besides these irregularly scattered tubuli, there are in the opercular valves of C. antennatus, innumerable smaller parallel tubuli, running to the external investing membrane.
Structure of the Radii and Alæ.—The radii, when developed, are always rather narrow. Their recipient furrows are generally nearly as broad as the radii themselves. Their edges are either quite smooth, as in C. antennatus; or very finely crenated; or, as in C. dentatus and Hembeli (Pl. 18, fig. 3 a, 5 a), so strongly crenated as to make the suture, both externally and internally, toothed: in these two species, the radii are ribbed in transverse lines parallel to the basis, each rib corresponding with one of the projecting and interlocking teeth on the sutures. In C. intertextus, and much less plainly in most specimens of C. scabrosus (Pl. 19, fig. 1 a, 2 a), we have a structure in appearance very different, for the radii here consist of several very oblique plates, (i. e. nearly parallel to the parietes) on both sides of the sutures, which are interfolded or locked together: I believe that this structure is a mere modification of that in C. dentatus and Hembeli, the transverse ridges on the radii of those species being here developed into oblique plates. We shall hereafter meet with a similar structure in the genus Verruca; to which genus, until meeting with these two species of Chthamalus, I had thought that the interfolding sutures had been confined. The alæ have their edges generally finely crenated: during diametric growth (when such takes place), they are rarely added to above the level of the opercular membrane, and hence their summits are oblique: in C. intertextus, however, the alæ are laterally added to above the opercular membrane, and their recipient furrows are likewise added to, of which fact I have seen no other distinct instance in any genus; hence on both sides of the sutures, in the sheath of this species, the lines of growth are upturned. In some much disintegrated specimens, both of C. stellatus (var. depressus) and of C. antennatus, the radii have been corroded away, and the diametric growth is effected exclusively by the growth of the alæ, which are moreover much exposed, and rendered conspicuous. The sheath descends a moderate distance down the shell. When a shell is boiled in potash, the sutures (excepting when abnormally calcified together, as very often happens with some species) always fall apart, showing that the union is simply by animalised matter.
Basis.—The basis is always membranous; but we have seen, in C. intertextus, that the walls form a flat ledge all round the base, and that in old specimens of C. Hembeli, they grow so far inwards and become so completely confluent, that they might most easily be mistaken for a true calcareous basis. I may add, that in one elongated specimen of C. stellatus from La Plata, the walls had likewise grown rectangularly inwards, forming a flat base, and had then turned upwards in the middle, forming a medial crest, with the edges not quite calcified together. The true basal membrane is very obscurely divided into concentric slips. I observed in several species, attached to the lower surface, an excessively fine network, quadrangular or hexagonal, of yellow vessels, which seemed insensibly to pass into the sheets, discs, and globules of cement, by which the membranous basis adheres to the supporting surface. I saw, in C. antennatus, numerous irregular, bifurcating, and inosculating cement-ducts, of unequal diameter, often crossing each other, and sending off branches ending in points: the older ducts, instead of being solidly filled up with cement, were only divided by septa. I did not succeed, in any species, in discovering the cement-glands.
Mouth.—The labrum is slightly bullate, with the middle portion depressed, but not forming a notch; in some species it is hairy, and in some pectinated with short spines. The palpi are of moderate size. The mandibles have from three to five main teeth, the number sometimes varying even in the same species: the lower teeth are either plainly double laterally, or very obscurely double, or to all appearance quite single: a rather large lower portion of the mandible is finely pectinated. The maxillæ are always notched under the two or three large upper spines: the notch bears some fine spines: beneath the notch there are some large spines, and at the inferior angle some smaller ones.
Cirri.—The first and second pairs are always very short compared with the four posterior pairs. The rami of the first pair are slightly unequal. The third pair, in length and arrangement of the spines, very closely resembles the three posterior pairs; in C. intertextus, however, the few basal segments, chiefly on the anterior ramus, are thickly clothed with bristles, like the segments of the second cirrus. In C. antennatus (Pl. 29, fig. 2), the anterior ramus of this same third pair is usually (one single specimen being excepted) much elongated, having at least twice as many segments as the posterior ramus, but the number is variable; and these segments, either all, or only the upper ones, instead of having their spines regularly arranged in pairs, in a double row, are surmounted each by a circle of spines: I suspect that these elongated rami of the third cirrus act as antennæ. It can hardly be an accidental coincidence, that certain genera, as Lysmata and Pandalus, amongst the Macrourous Crustaceans, have the same leg (homologically the second thoracic limb) elongated and antenniformed. Certain varieties of C. stellatus and cirratus, also, have the anterior ramus of this same third cirrus considerably elongated. We are thus reminded of the remarkable variability in the numbers of the segments, and in the arrangement of their spines, in the cirri of Tetraclita porosa; in that species, however, it was chiefly the terminal segments of the posterior ramus of the third cirrus which were so highly variable. The three posterior pairs of cirri in Chthamalus support from three to five pairs of main spines on each segment, the number often varying in the same species, with some minute intermediate bristles. The dorsal surfaces of these segments, in some of the species, are serrated in an upward direction.
Body, &c.—The body does not present any particular character: in C. scabrosus there is a slight ridge running from the base of the first cirrus towards the adductor scutorum muscle: this ridge is clothed with a few hairs; there are also some hairs at the carinal end of the sack. In C. dentatus, also, there are hairs on the outer tunic of the prosoma. In two species which I opened, there were no cæca to the stomach. The ova vary in length from 13 to 14/2000th of an inch in length; they are packed in two lamellæ lying on each side of the animal’s body. The larva just escaped out of the egg, in C. stellatus, scabrosus and dentatus, had a large probosciformed mouth.
Branchiæ.—These present a very singular amount of difference within the limits of the same genus. In C. stellatus and antennatus we have a simple fillet, tapering a little, barely plicated, and about half, or more than half, as long as the sack; in C. scabrosus the branchiæ are entirely aborted, or are perhaps represented by the slight hairy ridge at the carinal end of the sack: in C. dentatus, on the other hand, each branchia consists of two large folds, barely plicated, almost covering the whole side of the sack, so that here the branchiæ are developed to an unusual degree, more than in Balanus, and as in Coronula and its allies: in the same manner as in these latter genera, the outer fold is considerably larger than the inner fold.
Affinities.—C. intertextus is the most distinct species of the genus, as shown by the peculiar radii and alæ, by the scuta and terga being calcified together, by the character of the third pair of cirri, and by the inflected parietes forming a ledge round the membranous basis; but in this latter respect C. intertextus resembles C. Hembeli. C. Hembeli, in its serrated radii, is closely related to C. dentatus; and this latter species differs in the structure of its radii only in degree from certain varieties of C. stellatus. Lastly, C. intertextus, in its peculiar radii, closely resembles C. scabrosus, and this latter species does not differ much from the other species. Hence the genus Chthamalus has no claims to be subdivided into smaller genera.
Range.—The species are found all round the world, from (as far as I have seen) 54°-55° north, to Cape Horn, in 55°-56° south. All the species, of the habits of which I know anything, are littoral; and in many parts of the world are excessively numerous, quite covering large spaces of the coast-rocks, and often coating the coast-shells. Chthamalus dentatus is littoral, like the other species; but it often lives attached on Balanus tintinnabulum and amphitrite, on the bottoms of ships arriving in British ports from the west coast of Africa. I do not know of any instance of more than two species occurring in the same region. Some of the species have large ranges: C. scabrosus extends from the Falkland Islands and Tierra del Fuego to Peru; and C. stellatus has an enormous extension over almost the whole world, excepting the west coast of South America and Australia. I do not believe any species of the genus, owing probably to their littoral habits, have hitherto been found fossil.
LEPAS STELLATA. Poli. Testacea Utriusque Siciliæ (1795), Tab. 5, fig. 18-20.
---- DEPRESSA (var.) Ib., Tab. 5, fig. 12-16.
CHTHAMALUS STELLATUS. Ranzani. Memoire di Storia Naturale (1820), Tab. 3, fig. 21-24.
-------- GLABER (var.) Ranzani. Ib.
-------- STELLATUS. Philippi (!). Enumeratio Mollusc. Siciliæ.
LEPAS PUNCTATUS. Montagu (!). Testacea Britannica (1803).
Shell white or gray, generally much corroded and punctured: radii (when present) narrow, with their sutural edges most finely crenated; tergum with the crests for the depressor muscle depending barely beneath the basal margin.
Var. (a, communis) fig. 1 a, 1 f: Shell conical depressed, upper part corroded, walls folded, sutures moderately plain or obliterated; radii not developed; orifice broadly oval.
Var. (b): Shell elongated, sub-cylindrical; sutures obliterated; surface much corroded; orifice almost circular.
Var. (c, communis) fig. 1 c, 1 e, 1 h: Shell conical, folded, sometimes covered by membrane; radii developed, narrow; orifice sub-hexagonal, toothed.
Var. (d, fragilis) fig. 1 d: Shell conical, smooth, thin; compartments easily separable, pale-coloured; radii developed, narrow; orifice large, toothed, sub-hexagonal.
Var. (e, depressus) fig. 1 b, 1 g, 1 h: Shell much depressed, surface much corroded, smooth: alæ largely exposed, marked by lines of growth: radii not present; parietes on the under side often supported by pillars; orifice sub-hexagonal.
Hab.—Southern shores of England, Ireland, Isle of Man, Mediterranean, Madeira, Cape de Verde Islands, Southern United States (Charlestown), West Indies, Brazil (Bahia), Rio Plata (Guritti Island), Red Sea, Philippine Archipelago, Coast of China, Gulf of Corea, Oregon or Northern California.
This species is very widely distributed and extremely common. On the coast-rocks of the southern shores of England it is, in parts, even more numerous than the Balanus balanoides, with which it often grows mingled. As already stated, it is often confounded in British collections with this species of Balanus, under the name of Balanus punctatus; that Montagu had this Chthamalus in view, when describing his Lepas punctatus, is certain, from his original specimen in the British Museum, but whether this was the case with his predecessor, Pulteney, in the Dorset Catalogue, I do not feel so sure. Chthamalus stellatus varies, as we shall immediately see, extremely in appearance. Some of the varieties, as var. depressus, which in external aspect are especially distinct, I have no doubt are really varieties, but whether this is the case with some of the forms from the more distant localities, is a little more doubtful; but I beg that it may be observed, that I have, in the case of every one of the varieties, and of all the specimens from distant localities, cleaned with potash and most carefully examined the disarticulated valves, and likewise dissected the included animal’s body.
General Appearance.—British specimens are usually conical, and have their walls folded, corroded in their upper parts, with the radii not developed, and the sutures more or less obliterated; in this state the orifice of the shell is entire, and very broadly oval: I have seen specimens in this condition from Madeira, Brazil, and the Gulf of Corea. The shells when crowded, are rendered cylindrical, and more or less elongated, with the sutures as viewed externally quite obliterated; the surface rugged and much disintegrated; and the orifice nearly circular: in this extreme condition I have seen specimens from England, from near Genoa, and from the mouth of the Plata: the specimens from these last two localities were of remarkable size, being half an inch in diameter, and rather more than half an inch in height. Again, other British specimens (fig. 1 c), though not nearly so common, are rather steeply conical, and have not only their sutures distinct, but narrow radii are plainly developed on apparently both sides of the sutures; in this case the orifice is slightly toothed, and is rather elongated: I have seen specimens in this condition, but with their walls rather more deeply folded, from the Cape de Verde and Philippine Archipelago. Other specimens, from some unknown tropical sea, differed only in the walls being but slightly folded, and being so perfectly preserved as to be externally covered with membrane: this latter circumstance gave the specimens a peculiar appearance. In this condition were some specimens (fig. 1 d) attached to oysters sent to me by Professor Agassiz, from Charlestown; and which differed from all the others that I have seen, in the thinness and smoothness of their compartments, and in the facility with which the compartments separated from each other and from the surface of attachment: hence I have called this form, which, until finding more important differences, I must rank as a variety, fragilis: it has stronger claims than the other varieties to be specifically separated; but I suspect that it has been exposed to some peculiar modifying conditions.
Lastly, we have the variety (fig. 1 b) excellently figured and described by Poli, under the name of L. depressa: this is much depressed, with the walls thin, not folded, with the surface much corroded, with the sutures very distinct, with the radii not at all or barely developed, but with the alæ largely developed, and marked with lines of growth, resulting from the diametric growth of the shell: the orifice is hexagonal, but broadest towards the carinal end: most of the specimens, but not all, have on the under sides of their compartments rugged pillars depending from beneath the alæ, for the purpose, apparently, of supporting the much depressed shell. This much depressed variety attains a larger basal diameter (but not a greater bulk or internal capacity) than any other variety, namely, sometimes three quarters of an inch. The great peculiarities of this variety result, apparently, from its much depressed form, deeply corroded not folded walls, and considerable diametric growth; from the latter cause the alæ are largely developed; as I can find neither internally nor externally any fixed diagnostic character I have not hesitated to rank this form as a variety. Poli found his specimens mingled with the ordinary C. stellatus, on the shores of Sicily; and I collected at St. Jago, in the Cape de Verde Archipelago, some specimens nearly as well characterised, also associated with the common variety.
The shell itself is dirty-white or gray, or brown: in some varieties, however, the white is nearly pure: internally the parietes are generally tinted dull purple. The corium of the sack is dark greenish-black, with a white edge to the lips lining the aperture between the opercular valves.
Structure of Shell and Radii, &c.—The under side of the parietes is either quite smooth, or marked with slight, branching, depressed lines; or mamillated; or irregularly studded with large pores. I have already alluded to the pillars, depending from the under sides of the alæ in most specimens of var. depressus: these pillars tend to form ridges, parallel to the sides of the compartment, like those we shall presently see in certain specimens of C. scabrosus. The radii are very narrow, when best developed; their edges, when disarticulated, can be seen, when examined by a strong lens, to be finely crenated. The edges of the alæ are likewise very finely crenated.
Scuta.—The outline of these valves varies considerably in specimens taken out of the same group: we have either a nearly equilateral triangle (fig. 1 f) or the tergal margin (1 e) is much shorter than the other margins. There is always a deep depression for the adductor muscle, and a small pit of very variable depth for the lateral depressor. But the tergal margin offers the greatest variability; here we see a very prominent articular ridge or fold, having either a straight edge or a single or double prominence (fig. 1 e-1 h). In specimens in the same group we find considerable variation in these points; but the amount of difference is sometimes so great, that I long hesitated whether to rank some of the varieties as species. The Terga, likewise, vary greatly in shape and width: in some of the commonest varieties (and in var. depressus) the valve is very narrow, with the under surface channelled or concave: in other varieties the valve is much broader and flatter. The spur is but slightly developed. The crests for the depressor muscles barely descend beneath the basal margin of the valve. The articular ridge, in some varieties (as in specimens from Madeira and the Cape de Verde Islands), is extremely prominent and straight (1 f); in others, it is little prominent and deeply sinuous (1 h). This great variability in the articular margins of the scutum and tergum seems to be mainly due to the corrosion to which these valves have been subjected, and their consequently modified growth: in some specimens the articular ridge of the scutum, and in others that of the tergum, has been largely developed, in either case their mutual outlines being greatly affected.
Branchiæ.—These are narrow, hardly at all plicated, elongated, being about half as long as the sack. In a specimen from La Plata, this organ ended rather more abruptly in a point than it did in other specimens.
Mouth.—The crest of the labrum is usually hairy, but in a specimen from Bahia (Brazil) there were some very fine teeth. The palpi vary somewhat in shape, and sometimes have a row of bristles along their basal exterior margins. The mandibles usually have four main teeth, the lowest one being confluent with the inferior pectinated angle: in var. depressus, in the same individual, there were only three teeth on one side of the mouth and five on the other; the lower main teeth are laterally double, but generally one tooth of each pair is so small and obscure as to be perceived with difficulty. In the maxillæ, there are some large spines above the notch, and in the notch some fine ones: in var. depressus, and in a cylindrical var. from La Plata, there was quite a tuft of small spines above the notch.
Cirri.—The outer surface of the pedicel of the second cirrus bears a tuft of long, fine, plumose hairs: the terminal segments of the rami of this cirrus sometimes (as in the La Plata specimens) support a clump of coarsely pectinated spines. In specimens having six segments in the shorter ramus of the second cirrus, the shorter ramus of the third cirrus had fifteen segments. The two rami of the third cirrus are usually equal in length and in the number of their segments; but in the Brazilian specimen there were fifteen segments in the posterior, and twenty-six in the anterior ramus; in another specimen, fixed on a tropical Perna, there were in the two rami of this third cirrus eighteen and twenty-four segments. In the three posterior pairs of cirri each segment carries either four or five pairs of main spines: the segments vary a little in the degree to which they are elongated, being most elongated in the var. from La Plata, with an elongated shell.
Varieties.—It will have been observed, that the shell, in the specimens from several distant quarters of the world over which this species, as I believe, ranges, differs considerably in external aspect: so do the opercular valves; and so do the parts of the mouth and cirri: but I cannot make out that these differences are coordinated. Thus, var. depressus, which is so entirely different from the others in appearance, differs only internally in the presence of a tuft of fine spines above the notch of the maxillæ; and this character is found in the La Plata variety, which, as far as the shell and opercular valves are concerned, is at the other end of the scale of variation. Again, var. fragilis, from Charlestown, presents, in the animal’s body, hardly any difference. The Brazilian specimens, which in the shell and operculum offer only quite common characters, have the remarkable peculiarity of a considerable difference in the length and number of the segments in the rami of the third cirrus; they, also, have the segments of the sixth cirrus considerably elongated, and the labrum finely toothed. Of these peculiarities one alone, namely, the inequality in the rami of the third cirrus, but in a lesser degree, is common to the specimens adhering to the tropical Perna, which had a shell very unlike the Brazilian variety, but which, on the other hand, differed scarcely in a single character from some other specimens from an unknown tropical sea, in which the rami of the third cirrus were quite equal. The La Plata specimens differ most in internal characters, viz., in the tuft of fine spines above the notch of the maxillæ, in the coarsely pectinated spines on the tips of the second pair of cirri, in having the segments of the sixth cirrus much elongated, and in the apex of the branchiæ being abruptly pointed; yet in the shell and operculum they were identical with certain Mediterranean varieties. From these several facts, I must believe that all the widely distributed forms here grouped together, do really belong to the same species.
Shell conical, generally smooth: when not deeply corroded of a pale dirty flesh-colour: sutures always distinct: radii, when present, with their sutural edges quite smooth.
Hab.—New South Wales, (Moreton Bay, 27° S.; Sydney; Twofold Bay), Van Diemen’s Land (Hobart Town). Attached to littoral rocks and shells; Mus. Brit., Cuming, Darwin.
General Appearance and Structure of Shell.—Shell conical, rather smooth; when not much corroded, of a pale dirty flesh-colour; often covered by membrane; sometimes deeply corroded, extremely rugged, and then of a brown colour; in this condition not much punctured, as generally is the case with C. stellatus. Sutures almost always quite distinct; rarely the shell becomes cylindrical with the sutures obliterated. Orifice moderately elongated, sub-hexagonal. Radii rather narrow, but not so narrow as in C. stellatus, smooth, with their upper margins very oblique: when disarticulated their edges are quite smooth. The edges of the alæ are sometimes crenated, and sometimes not so, being only marked by lines of growth; they are often rather thick. The parietes are usually rather thick, with their internal surfaces smooth, and not mamillated, as is so often the case with C. stellatus. The largest specimens which I have seen, were .6 of an inch in basal diameter.
Opercular Valves.—These are hardly distinguishable from those of C. stellatus. The only very slight difference which I can point out is, that the crests for the tergal depressores are less spread out, and depend rather more beneath the basal margin of the valve; and lastly, that the surface of the tergum, just above these crests, is rather prominent.
Branchiæ: these are oblong; taper but little, and have a broad rounded end: they are scarcely plicated.
Mouth.—The crest of labrum is hairy: the palpi are square, and have no bristles along their basal exterior margins, but long ones at their truncated ends. The mandibles have three or four main teeth apparently single: the inferior coarsely pectinated portion is short. The maxillæ are deeply notched.
Cirri.—The first and second pairs, and portions of the third, are darker coloured than the three posterior pairs. The rami in both of the first two pairs are slightly unequal in length. The third cirrus is much longer than the second: in a specimen in which there were six segments in the shorter ramus of the first and second pairs, there were twenty segments in the posterior and shorter ramus of the third cirrus; and in this same individual there were no less than forty-nine segments in the anterior ramus. In another specimen (Pl. 29, fig. 2) the number of segments in the two rami of the third cirrus, was 20 and 41; in another, the numbers were 18 and 53; in several other specimens the numbers varied in about these proportions; but in one single specimen the numbers were equal. Not only did the number of segments thus vary in the two rami, but likewise the arrangement of the spines on the segments in the anterior and longer ramus; in some specimens the spines on all the segments were arranged in a single circle, and then the organ had a specially antenniformed appearance: in other specimens, some of the lower segments (in one case thirteen in number) had the spines placed in regular pairs precisely as on the posterior ramus, and as on the three posterior pairs of cirri. Under the genus I have pointed out the resemblance between this structure and that occurring in certain Macrourous Crustaceans. The pedicel of the third cirrus had its spines more crowded and irregular than on the three posterior pairs of cirri. The segments in the latter vary in bearing either three or four pairs of main spines. The whole dorsal surfaces of the lower segments of the several posterior cirri are serrated in an upward direction by short spines, but to a variable degree.
Shell white or gray: sheath and opercular valves generally clothed by fimbriated membrane: tergum, with its basi-carinal angle depending and pointed.
Hab.—Peru, Chile, Chiloe, Northern Chonos Islands. Attached to littoral rocks, and sometimes to littoral shells, often mingled with Chthamalus scabrosus; Mus. Brit., Cuming, Darwin.
General Appearance and Structure of Shell.—Shell dirty white or gray: sometimes tinted pale purple within; irregularly conical, or much depressed, or cylindrical and much elongated. Generally much corroded, sometimes well preserved and covered by membrane. Orifice rather large, of variable shape. Sutures often quite obliterated. Radii when developed narrow, with their sutural edges, as well as those of the alæ, generally very finely crenated, but to a variable degree. The membrane lining the sheath and covering the opercular valves, is remarkable from each zone being fimbriated; for this expression is more correct than to say that the membrane bears a row of spines, though the fimbriæ do approach in character to spines; sometimes, though rarely, the fimbriæ are branched. The largest specimens which I have seen (from Coquimbo and Valparaiso) were half an inch in basal diameter, and some of these were so much elongated as to be one inch in height.
Scuta.—The scuta are rather narrow: they have a somewhat peculiar appearance, from the articular furrow being wide, and from the articular ridge projecting with a uniform curvature: the pit for the lateral depressor muscle has some minute crests, of which I have seen traces in the foregoing species. The Terga vary somewhat in shape: they have the basi-carinal angle of the valve, where the narrow crests for the depressores are placed, pointed and dependent, and the surface of the valve above these crests is prominent. Altogether the opercular valves have a sufficiently distinct character to be recognised without much difficulty.
Mouth.—The crest of the labrum is not toothed; the palpi have long hairs along the exterior basal margin. The lower main teeth of the mandibles are plainly laterally double. Cirri.—The pedicel of the second cirrus is extremely broad, and on the exterior margin supports a tuft of very long, finely plumose spines: in some specimens each of the lower segments of the anterior ramus of this cirrus bore one or two very large spines, doubly and extremely coarsely pectinated. In two specimens the rami of the third cirrus were of equal length: but in one specimen (from Iquique, Peru), having seven segments in the shorter ramus of the first and second pairs of cirri, the posterior ramus of the third pair had fourteen segments, and the anterior ramus twenty-two segments. The posterior cirri have segments carrying five pairs of main spines: the dorsal surfaces of the lower segments are serrated.
Shell brownish, plicated; orifice twice as long as broad: tergum triangular, equilateral, with the basal and carinal margins slightly protuberant.
Hab.—California, attached to Lottia grandis. Peru(?); Mus. Brit.
General Appearance and Structure of Shell.—Shell globulo-conical, irregular, with the walls much folded. Colour brownish. Sutures generally distinct in young specimens, and nearly obliterated in full-grown individuals. Radii, when present, very narrow. The orifice of the shell, in full-grown specimens which have their summits a little worn, is narrow, much elongated, about twice as long as wide, oval or ovate, with the rostral end the narrowest: the elongation of the orifice offers almost the only character by which this species can be externally recognised. The lateral compartments are rather wider than usual in proportion to the rostro-lateral compartments. Basal diameter of largest specimen .2 of an inch.
Scuta, elongated transversely, with the pit for the adductor muscle bordered on the under side by an adductor ridge rather more prominent than usual in this genus. Terga, triangular, equilateral, with the margins slightly curved and protuberant: the basal margin is regularly and equably curved from one end to the other.
Neither the Mouth nor Cirri offer any peculiar characters distinct from the genus. I may mention, however, that the crest of the labrum is toothed, and that the segments of the posterior pairs of cirri support five pairs of main spines.
The characters by which this species differs from C. stellatus and from the other species, consist almost exclusively in the triangular and equilateral terga, and in the much elongated orifice of the shell; and these differences I believe to be of specific value. I must, however, confess that I have examined one young specimen attached to a Pollicipes elegans, in which the orifice was not nearly so much elongated, and in which the terga were not so equilateral, with the basal margin not quite equably curved, but more protuberant on the scutal than on the carinal side: from an examination, however, of only one specimen, and that a young one, I cannot decide on its specific nature.
CHTHAMALUS DENTATUS. Krauss (!). Die Südafrikanischen Mollusken, 1848, tab. 6, fig. 27.
Shell dirty white or brownish: sutures formed by interlocking teeth: tergum with the carinal margin protuberant.
Hab.—South Africa, Natal; West Africa, Loanda and the Gold Coast; West Indies (?). Attached to ships’ bottoms and to littoral shells, and to Tetraclita serrata, Balanus perforatus, and amphitrite; often attached to Balanus tintinnabulum and amphitrite on ships’ bottoms.
General Appearance and Structure of Shell.—Shell dirty white, pale brown, or gray: conical, moderately depressed: walls either broadly and irregularly folded (fig. 3 a), with the surface corroded, or (when attached to ships’ bottoms and sometimes to other Cirripedes) narrowly and regularly folded (3 b), with the surface well preserved, smooth, and generally covered by thin brown membrane. These latter specimens generally have the shell more steeply conical, with the orifice rather smaller, and the radii broader, than in the first-mentioned specimens, which are attached to coast-rocks and shells, and have had their summits worn down. The sutures in all cases are tolerably distinct, and have their edges toothed and interlocked: the crenations are visible before the compartments are disarticulated, when viewed either internally or externally, but occasionally they are obscure. The radii, when best developed, are rather narrow, and of equal width on both sides of the sutures, with their summits rounded: their surfaces are finely ribbed transversely, each rib corresponding with, or rather forming a point of, the toothed edge. On the under side these teeth usually are a little hollow or are pitted: the radii, in fact, may be said to be folded, like the parietes, only more symmetrically and narrowly, so that the points in the opposed edges interlock. The edges of alæ are serrated, but more finely than the radii. The parietes are rather thin, with their under surfaces generally smooth. The sheath does not descend far down the shell. The colour of the corium lining the sack and the animal’s body varies considerably, being either almost black or pale purple; and the specimens adhering to ships’ bottoms are internally almost white. Of these latter specimens, I have seen some .6 of an inch in basal diameter: of corroded specimens attached to littoral shells, I have not seen one quite .4 of an inch in basal diameter.
Scuta, with the articular ridge very prominent: the pit for the adductor is deep, and there are generally some distinct, though minute, pits for the lateral depressores. The Terga (fig. 3 c) have the articular ridge very prominent; and the carinal margin is rather more arched and protuberant than in the other species.
Mouth.—The crest of the labrum is toothed: the palpi are short, truncated, with long spines arising from their ends, and along the basal exterior margin. In the mandibles the first tooth is seated rather far from the succeeding teeth: the inferior part is coarsely pectinated: the maxillæ are deeply notched. The tips of second pair of Cirri have many coarsely pectinated spines: the shorter ramus had six segments, whilst the shorter ramus of the third pair had eighteen segments: the segments on the posterior cirri carry five pairs of main spines.
Branchiæ, &c.—These consist of a double fold, the outer one being the largest, and the inner semi-circular, as has been described under the genus. In a young specimen, only one tenth of an inch in basal diameter, the branchiæ consisted of a single fold; in a specimen a little larger, there were two folds, but these were of equal size: ultimately the outer fold increases in size so as to become nearly double the inner fold. The Ovarian tubes are remarkable from their large diameter. I was surprised to observe in the specimen only one tenth of an inch in basal diameter, that the larvæ were ready to escape. On the prosoma, there are some longish hairs arranged in short rows, and some few on the membrane lining the sack, and some on the opercular membrane and valves.
It may be seen in Pl. 18, fig. 3 a, and 3 b, that I have here united two varieties considerably different in external aspect: I have done this without hesitation, inasmuch as there are intermediate forms, and as the differences are analogous with those so commonly occurring in sessile cirripedes; dependent on whether or not the specimens have been exposed to corrosion. I have seen both varieties from Natal, and both from the west coast of Africa; although the smooth, well-preserved, narrowly plicated varieties seem more common in western than in southern Africa. With respect to the range of the species, I have seen a specimen from the West Indies, but it was the variety which so commonly adheres to ships’ bottoms. This variety often arrives alive in British ports; and I have seen a specimen picked up dead on the beach near Dublin.
EURAPHIA HEMBELI. Conrad. Journal Acad. Nat. Sc. Philadelphia, vol. 7, 1831, Pl. 20, fig. 6.
Shell dull reddish purple: sutures, when not obliterated, formed by interlocking teeth: basis sometimes rendered calcareous by the inflexion of the parietes: scutum with two or three furrows extending down the middle of the valve.
Hab.—California, near S. Diego, according to Conrad. Mus. Brit., Cuming.
I have seen five, old, large specimens, from an unknown locality, with their whole surfaces deeply corroded, and with most of the sutures obliterated; and three separated valves of a young specimen. From these materials, imperfect as they are, I feel no hesitation in identifying this species with the Euraphia Hembeli of Conrad, which is remarkable in several respects, and especially from being gigantic in size, compared to other members of its sub-family.
General Appearance and Structure of Shell.—The young specimen (fig. 5 b, about .7 of an inch in basal diameter) consists only of the carina, and the two lateral compartments; but these, as far as I can judge, resemble the specimen figured and described by Conrad, which was two inches in diameter. Shell depressed, spreading, surface moderately smooth, covered by brownish membrane: shell itself pale dull reddish-purple. The radii are not very narrow, with their summits rounded and very oblique: their edges are toothed, and their external surfaces are transversely ribbed, in correspondence with the interlocking points of the sutures. On the internal surface, the toothed suture is not visible, except near the base of the shell, owing to the overlapping of the alæ. The alæ have oblique summits, which are slightly notched owing to the upturned prominent lines of growth. The parietes are thick; their basal internal surfaces are rugged, with slightly branching ridges.
The old specimens (fig. 5 a) are so much corroded that not a particle of the external surface is left: one of them which was 2-3/4 of an inch in basal diameter. Shell much depressed, spreading; colour pale purple; orifice large, rhomboidal, with a slight hollow on each side for the corners of the scuta: sutures generally in part or wholly obliterated; where still preserved, the interlocking toothed structure is distinct; the sheath is strongly marked by lines of growth, and is of a dark brown colour. The carina and rostrum are of unusually large size compared with the lateral compartments; and this, as far as I can judge, must have been the case with the younger specimens. That portion of the rostro-lateral compartment which forms part of the sheath, is reduced to a mere ridge. The most remarkable character is, that all these old specimens (of which the smallest measured nearly one inch and a half in diameter) had a flat, wide, calcareous basis, which is absolutely continuous with the inner lamina of the parietes, whereas in the younger specimen there was no appearance of any tendency in the parietes thus to grow inflected. There can be hardly any doubt that in a series of specimens some would be found with the parietes first forming a flat narrow ledge round the true basal membrane (as in the following species); and that in others, this ledge would be wider and wider, till its edges met in the middle, and coalesced into a continuous plate.
Opercular Valves.—I have seen these only in the old corroded specimens (fig. 5 c, 5 d): they are locked together by remarkably strong articular ridges and furrows.
The Scuta have externally two or three impressed lines or narrow furrows, proceeding from the apex to the middle of the basal margin; these can be seen only in one of my specimens, owing to the degree to which the valves have suffered disintegration; but they are mentioned by Conrad. The basal margin is rather short compared with the other two margins. The tergal margin is remarkable from the depth of the upper furrow above the articular ridge, and from the size of the prominence (appearing like the true apex of the valve) above this upper furrow. There is a hollow for the adductor muscle, and traces of crests for both the rostral and lateral depressores. The Terga are generally but little corroded, and hence the dark brown membrane with which they are covered is well preserved; the shelly matter itself is also brown: there is only a trace of this colour in the more corroded scuta: the external surface of the terga is very smooth. The spur is pretty well developed, and is half as wide as the whole valve. The lines of growth are upturned along the carinal margin. The articular ridges and furrows are much developed. The crests for the depressor muscles are extremely strong; they depend beneath the basal margin, and are remarkable (fig. 5 c) from being furnished each with fine sub-crests.
Animal’s body, unknown.
Shell, when well preserved, violet-purple: sutures, when not obliterated, formed by oblique interfolding laminæ: basis membranous, but surrounded by a ledge formed by the inflected basal edges of the parietes: scutum and tergum completely calcified together.
Hab.—Philippine Archipelago; Mus. Cuming.
General Appearance and Structure.—Shell depressed, with a large diamond-shaped orifice. Colour beautiful violet-purple, but externally much obscured by disintegration, causing the shell to be ashy gray. Walls smooth or slightly folded. Sutures generally quite, or almost quite obliterated; but when well preserved, they differ remarkably in appearance from those in the foregoing species; for the radii externally here consist of oblique plates or laminæ arising on both sides of the sutures, standing nearly parallel to the parietes, and interfolding with each other. These laminæ are rather plainly marked by lines of growth. Essentially the radii do not differ much from those in C. dentatus and Hembeli; we have but to produce obliquely upwards the transverse and interlocking ribs on their radii, and so convert them into laminæ. During the diametric growth of the shell, the sutural edges of the alæ are added to, in the usual manner, by upturned lines of growth; and, in addition, the recipient furrows of the alæ are similarly added to, so that the lines of growth are upturned, and alæ appear to have been developed on both sides of the sutures in the same way as the radii appear to have been developed on both sides in many Chthamalinæ, though rarely in the Balaninæ. The inside of the shell is beautifully coloured rich violet; it is punctured with small holes as so often is the case with C. stellatus. In every specimen (all full-grown) which I opened, the inner basal edges of the parietes were inflected rectangularly inwards, forming a smooth-edged ledge all round the basal membrane, which, in proportion to the width of this ledge, was by so much reduced in diameter. The largest specimen which I have seen was .35 of an inch in basal diameter.
Opercular valves.—The scuta and terga, in all the specimens which I have seen, were firmly calcified together; in some, a trace of a suture could be seen externally, but hardly a trace internally. In one specimen, there were vestiges of some impressed lines on the scutum, in exactly the same position in which such occur in C. Hembeli. The scutum is rather narrow. The basal margin of the tergum is either straight, or depends a little on the scutal side, thus producing a small spur: the crests for the depressor muscles are strongly marked, and depend beneath the basal margin.
Mouth.—The labrum is strongly toothed: the palpi have long hairs along the exterior basal margin: the mandibles have only three main teeth, and the inferior coarsely pectinated portion is short; the maxillæ deeply notched. Cirri: the first and second pairs have their rami slightly unequal in length; the third pair differs from the same pair in the other species of the genus, in having some few of the basal segments on the anterior ramus thickly clothed with spines, so as to be brush-like: there is even a trace of a similar structure in the lowest segments of the posterior ramus. In the three posterior pairs of cirri the segments are much elongated, and support four pairs of spines.
Branchiæ.—Unknown.
Shell (when well preserved) dull purplish-brown: sutures formed by oblique interfolding though rarely well developed: tergum with a deep narrow pit, at the basi-carinal angle, for the depressor muscle.
Hab.—Peru, Chile, Tierra del Fuego, Falkland Islands. Very common; attached to littoral rocks and shells, and often associated with Balanus flosculus, and sometimes with Chthamalus cirratus; Mus. Brit., Cuming, W. Dunker, Darwin.
General Appearance and Structure.—Shell generally depressed; when growing crowded, sometimes cylindrical: colour dingy purplish-brown, but when much corroded, dirty gray; very young shells are very dark green, owing to the corium, which is of this colour, being seen through the valves. Surface generally rugged, from irregular slight longitudinal folds, and from the transverse overlapping tile-like lines of growth; but sometimes the surface is nearly smooth, with very slight longitudinal folds, these being gray coloured, the intermediate parts being pale dingy purple, the shell thus becoming striped. Orifice rhomboidal, passing into trigonal, owing to the great width of the carinal end. Sutures generally very distinct, rarely obliterated in the cylindrical varieties. Radii narrow, generally exposing much of the alæ, which are plainly marked by lines of growth: the radii themselves, when well developed, which is not often the case, consist of small laminæ or ridges, placed on both sides of the sutures, and interfolded or interlocked together: usually only a trace of this structure is exhibited, but occasionally, along some or along all the sutures (as in the specimen figured), the laminæ of the radii interfold, as plainly as in C. intertextus. The alæ differ slightly from the alæ of the other species, in not forming so much of a rectangular projection, the lower margin running with a gentle curve into the parietes. The internal surface of the parietes is either smooth, or near the basal margin is roughened with depending points: in some specimens from the Falkland Islands, both edges of each suture were inflected, forming a double ridge, with roughened edges, resting on the basal membrane, and supporting the shell. I must mention that in my notes made at these Islands, I remark that the basal membrane seemed sometimes to be surrounded by a calcareous rim; none of the specimens brought home are thus characterised; but bearing in mind the affinity of this species to C. intertextus, no doubt we have here an indication of the shelly ledge surrounding the basis, as described under that species. The largest specimens which I have seen are a quarter of an inch in basal diameter.
The Opercular Valves generally have their summits much worn down. The scuta are elongated in the line of the longer axis of the orifice; the articular ridge is very prominent, and is placed in the middle of the tergal margin. The terga are very narrow, as in some varieties of C. stellatus: they are remarkable in two respects, namely, in the depressor muscle being attached to a plate, formed apparently by the union of the usual crests, parallel to the outer lamina of the valve itself, a deep narrow cavity (fig. 2 d, p) being thus formed; and secondly, in the far more extraordinary circumstance of the existence of a small pit (q) at the extreme basi-scutal corner of the valve, in which about half of the scutal lateral depressor muscle is attached: I have observed no other instance in any cirripede of the partial attachment of a muscle properly belonging to one valve to another valve. The figures of the valves 2 b, 2 c, 2 d, are from specimens most unusually perfect, with the upper portion not worn away; the ordinary appearance of the valves as seen from above, is given in fig. 2 a; at fig. 2 d, a view is given of the tergum seen from vertically beneath, showing the cavity for its own depressor muscle, and for part of the lateral depressor muscle of the scutum.
Mouth.—The crest of the labrum is hairy, without teeth: the palpi have long spines at the end, but none along the inferior margin: the mandibles have either four or five graduated teeth, the lower ones of which are plainly double laterally: the maxillæ have a very sinuous edge. Cirri: the first and second pairs are very short: on the four posterior pairs the segments support either four or five pairs of main spines, with the small intermediate spines rather larger than usual.
Branchiæ.—None; but where they ought to occur, there are two very slight ridges clothed with hairs, about the 1/100th of an inch in length. On the prosoma, there is a slight ridge, extending from the base of the first cirrus towards the adductor scutorum muscle, also clothed with hairs; this unusual character of the prosoma being hairy is common to C. dentatus.
This species is the commonest cirripede on the shores of the Falkland Islands: many of the specimens are there crowded together, and rendered elongated and cylindrical, with the walls very thin, and the sutures often obliterated; as the opercular membrane is very narrow, the opercular valves are much influenced both in their outline and in their crests and articulations, by the varying form of the shell: I have even seen specimens with the scutum and tergum on one side twice as large as on the other side.