A Monograph on the Sub-class Cirripedia · Charles Darwin
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31. BALANUS DECLIVIS. Pl. 7, fig. 4 _a_-4 _d_. _Parietes solid; rostrum nearly twice as long as the carina or carino-lateral compartments, hence the basis is oblique. Tergum with the spur truncated, half as wide as the valve._ _Hab._--West Indies; Mus. Brit.--Jamaica, imbedded in a sponge; Mus. Cuming. This is a remarkable species; when first seeing it imbedded in numbers in a sponge, I did not in the least doubt but that it was an Acasta: on examination, however, it is found to have a membranous basis, and therefore cannot by the definition enter into that sub-genus, to which, however, it is very closely allied. It differs from other sessile cirripedes very remarkably in the rostrum being nearly twice as long as the carinal compartments, so that the basis is always very oblique, or placed almost on one side; in this elongation of the rostrum, although in a different direction, we are reminded of _B. calceolus_ and its allies; and these latter we know can hardly be separated from certain species of Acasta. Hence the position of our present species in this section, is not natural; but I am unable to place it elsewhere, without breaking down every definition: it should stand somewhat isolated, on one side of a line of affinity connecting _Balanus calceolus_ and _navicula_ with _Acasta purpurata_.
_General Appearance._--The shell is thin, fragile, smooth, and white, but covered to a considerable extent by a brown membrane, which on the sheath and opercular valve is of a bright tint, and clothed with bristles. Viewed laterally, the rostrum is seen to be considerably bowed, and from its being nearly twice as long as the other compartments, with its lower end bluntly pointed, the basal margin of the whole shell is rendered very oblique, forming a slightly concave line. The lateral compartments are rather longer, and about one third broader than the carino-lateral compartments. The rostrum, from terminating downwards in a blunt point, instead of being square or truncated, as in all other Cirripedes, and from the upper end being, as is usual, pointed, has, when disarticulated from the other compartments, the shape of a boat. The parietes are not at all porose: their internal surface sometimes shows traces of longitudinal ribs, but sometimes there are none. The radii are narrow, with their summits very oblique, and their sutural edges smooth. The sutural edges of the alæ are likewise smooth. The largest of Mr. Cuming's specimens was .2 of an inch in diameter; but a disarticulated specimen in the British Museum must have been larger, having a rostrum .3 in length. The _Basis_ is membranous.
The _Scuta_ are rather convex; they have their lines of growth approximate, most finely crenated, so as to be very feebly striated longitudinally. Internally, the articular ridge is pretty well developed, its lower edge being very oblique; there is barely an adductor ridge: the pit for the lateral depressor muscle is deep. The spur of the _Tergum_ is placed close to the basi-scutal angle of the valve; it is about half as wide as the valve, with the lower end truncated: sometimes it may be rather said to be bluntly pointed, owing to its carinal side sloping up to the basal margin. The articular ridge is pretty well developed. The crests for the depressor muscles are barely discernible. _Animal's body_ unknown. _Section_ F. _Parietes and radii not permeated by pores; basis sometimes permeated by pores, sometimes not permeated, sometimes excessively thin and hardly distinguishable._ 32. BALANUS HAMERI. Pl. 7, fig. 5 _a_-5 _c_. LEPAS HAMERI. _Ascanius._ Icones rerum naturalium, Tab. 10, 1767. ---- TULIPA. _O. F. Müller._ Prodromus. Zoolog. Dan. 1776; sed non _L. tulipa_, in Poli, Test. ut. Siciliæ; neenon _B. tulipa_, in Bruguière, Encyclop. Method; neenon _B. tulipa_, in Sowerby, Genera of Shells. ---- TULIPA ALBA. _Chemnitz._ Syst. Conch. Tab. 93, fig. 832. ---- FOLIACEA. _Spengler._ Skrivter of Naturhist. Selskabet, 1 B. 1790. BALANUS CANDIDUS. (Tab. emendata) _Brown._ Conch. Great Britain (1827), Tab. 6, figs. 9 and 10, et 2d edit. Tab. 54, figs. 9-12.
_General appearance._--Shell tubulo-conical, very smooth, white, generally more or less covered by yellow thin membrane: orifice large, sub-triangular: radii moderately broad, with their more or less oblique summits slightly rounded and smooth; from this circumstance the shell has been justly compared to the half-opened flower of a white tulip. Specimens often exceed an inch in basal diameter; I have seen one from Scarborough two inches in diameter and one and three quarters in height: another specimen was 1.6 in diameter and 3 in height. The specimens in the glacial deposits seem even to have acquired larger dimensions, one from Uddevalla being nearly four inches in height. _Scuta_, elongated, flat, feebly striated longitudinally: internally, articular ridge short, moderately prominent: adductor ridge, confluent in the upper part with the articular ridge, running straight down and forming a rather large cavity for the lateral depressor. _Terga_ feebly striated longitudinally, with a longitudinal furrow, having the sides, in old specimens, partly closed in: the basal margin slopes much towards the spur, which is rather long and narrow, with its end rounded: it is placed at about its own width from the basi-scutal angle. Internally, articular furrow narrow; crests for the depressores moderately prominent, but in a variable degree. _Compartments_: these are unusually thin, and separate easily: the parietes are finely ribbed longitudinally on their insides; the bases of these ribs being just perceptibly denticulated. _Radii_, with their summits oblique (usually at about an angle of 45°), slightly arched and quite smooth: the smoothness is produced by the edge being a little inflected: sutural edge quite smooth, without even a trace of septa or denticuli. _Alæ_ oblique, generally rather less oblique than the summits of the radii: sutural edges smooth, with an excessively fine linear furrow running along the edge, a little towards the inner side, and filled with a yellow ligamentous substance: a furrow of this kind I have seen in no other species.
_Basis_, solid, not permeated by pores; either smooth, or slightly furrowed in lines radiating from the centre. _Mouth_: labrum with scarcely perceptible minute bead-like teeth thinly scattered along the edge. _Palpi_ and _outer maxillæ_ rather sparingly clothed with hairs. _Mandibles_ with teeth rather sharp; the fourth and fifth teeth small, but well developed; inferior angle pointed with fine spines. _Maxillæ_ with a deep notch under the two upper great spines. _Cirri_, the first pair is short, with rami of nearly equal length: the segments are not protuberant in front either in the first or second pairs. In the posterior cirri, the segments bear four pairs of spines, with a tuft of rather long intermediate spines: in young specimens there are only three pairs: the spines in the dorsal tufts are short and thin. When the shell is disarticulated, this species cannot be confounded with any other; but judging by external characters alone, it may sometimes be very easily confounded with _B. eburneus_, and I have received the two species under this one name from Massachussetts: generally _B. Hameri_ may be distinguished from _B. eburneus_ by the smoothness of the summits of its radii, and by the so-called epidermis being of a darker yellow. With respect to the fossil specimens from the glacial deposits, I have little to add; I have seen one from Uddevalla, as already remarked, four inches in height, and a lateral compartment broader by one fourth than the same compartment in any recent specimen. As Sir C. Lyell remarks (Phil. Transact.), the compartments are always found separated, which is accounted for by their weak union in a recent state. This species, when fossil, is usually associated with its deep-water congeners _B. porcatus_ and _crenatus_, as at the present day.
I must here mention that I have examined a considerable number of _separated_ compartments, without opercular valves, brought from Barbados, in the West Indies, showing the existence there of a closely allied or possibly identical species. The only difference which I can point out in these compartments is, that the parietes are rather thicker, and the radii rather narrower, with more oblique summits: some of the compartments are two inches in length. It seems very improbable that the true _B. Hameri_ should extend to the West Indies, but after what has been seen in the case of _B. crenatus_, this is possible. 33. BALANUS AMARYLLIS. Pl. 7, fig. 6 _a_-6 _c_. _Shell striped or clouded with pinkish-purple, or quite white; radii narrow, with their oblique summits smooth or arched: basis porose. Scutum plainly striated longitudinally: tergum with the spur narrow._ _Var._ (_a_):[99] _bright rosy pink, not distinctly banded longitudinally_. Hab. North-east coast of Australia. _Var._ (_b_): _snow white, glossy; orifice deeply toothed_. [99] This variety perhaps is the _B. roseus_ of Lamarck, as figured in Chenu, 'Illust. Conch.' Tab. 2, fig. 9; but as Lamarck does not even notice such conspicuous external characters as the longitudinal striæ on the scuta, and the smooth rounded edges of the radii, it is impossible to identify his species. _Hab._--Mouth of the Indus; East Indian Archipelago; Philippine Archipelago; Moreton Bay, and the north-east coast of Australia. Attached frequently on ships' bottoms, associated with _B. tintinnabulum_ and _amphitrite_. Sometimes attached to _Gorgoniæ_ with _B. calceolus_.
_General Appearance._--Shell steeply conical, with the orifice sub-rhomboidal, moderately large, very slightly, or deeply notched: surface very smooth: white, longitudinally banded with pinkish or leaden purple, with sometimes a purplish, sometimes a yellowish tint, the latter owing to the persistent epidermis; the bands are pale, and often fade away in the lower, and sometimes in other parts of the shell; the epidermis is generally more persistent on the narrow rounded radii than on the parietes, and hence the radii are generally yellowish. The opercular valves are pale dull purple: the sheath is darker purple, with the exception of the portions of the alæ added during the diametric growth, which are of a dead white, and are externally conspicuous. The scuta are striated longitudinally. I may remark, that, excepting the narrowness of the radii, with their quite smooth, rounded and very oblique summits, some specimens are hardly distinguishable, in external aspect, from varieties of _B. amphitrite_. If the specimens from the north-east coast of Australia, of which I have seen many (but unfortunately only one small one had its opercular valves), form, as I fully believe, merely a variety; it is characterised by its nearly uniform beautiful rosy pink, without any _distinct_ longitudinal bands: of these specimens I have seen one two inches in basal diameter, and three in height: of ordinary duller-coloured striped specimens, the largest was 1.7 in basal diameter. Of the perfectly white _var._ (_b_), I have seen several specimens, the largest being .6 of an inch in diameter: these have a somewhat peculiar aspect, but I have met with only one specimen with opercular valves, and that was extremely young: I at first considered this form as specifically distinct; but I can point out, after careful examination of the whole shell, operculum, and internal animal of the young specimen, no sufficient diagnostic characters.
_Scutum_, plainly striated longitudinally, with the striæ dividing the prominent lines of growth into squarish beads: internally, the upper part of the valve is roughened: the articular ridge is short, remarkably little prominent, and not reflexed; the adductor ridge is blunt and little prominent; sometimes it is almost confluent with the articular ridge: there is a deep but variable depression for the lateral depressor muscle; and in young specimens of _var._ (_a_) it was almost absent. _Tergum_: the surface exhibits traces of longitudinal striæ: there is a deep longitudinal furrow, with the sides folded in and quite closed in full grown specimens: the scutal margin is considerably curved towards the scutum. The spur is long and narrow, with the end bluntly pointed, placed at rather above its own width from the basi-scutal angle; the basal margin slopes but little towards the spur: the crests for the depressores are feebly developed. _Parietes_: their internal surfaces are strongly ribbed longitudinally, with the basal ends of the ribs coarsely denticulated, and with the denticuli extending close to the outer lamina. The radii are generally narrow, but their width varies; their summits are very oblique, smooth, rounded, and inflected, with the lines of growth, in the uppermost part, curving inwards; their sutural edges, in the upper inflected portion, are quite smooth, without septa; in the lower and larger portion, the edge is crenated with excessively fine teeth or septa, not denticulated: the radii, like the parietes, have no inner lamina: the recipient grooves in the opposed compartments are smooth, and are in the lower part of the shell of unusual depth. The _alæ_, differently from the radii, generally have their summits very slightly oblique, but sometimes they are highly oblique: their sutural edges are most finely crenated. The _basis_ is generally flat, sometimes cup-formed; it is permeated by pores, crossed by transverse septa; and sometimes there is an underlying cancellated layer.
_Mouth_: labrum with either six very small teeth, or with none. _Mandibles_ (Pl. 26, fig. 5), with the third tooth a little thicker than the first; fourth and fifth teeth small, but quite distinct. _Maxillæ_ (Pl. 26, fig. 7), with the inferior part forming a square step-formed projection, bearing, one behind the other, two spines as long as the upper pair; in a young specimen of _var._ (_a_) this step-formed projection was absent. _Cirri_: first pair with the rami unequal by about four segments: the shorter ramus has the segments very protuberant in front, thickly clothed with strongly serrated spines; the second cirrus has segments moderately produced; the third has them produced only in a slight degree. The pedicels of the second and third cirri have dorsal tufts of spines, but not a hairy plate prolonged over the thorax. The posterior cirri have segments broader than long, bearing only two pairs of nearly equally long spines; and between each pair there is a small intermediate tuft. The penis has the usual basi-dorsal point. _B. amaryllis_ is a distinct and well-defined species, more nearly related to _B. Hameri_ than to any other form. 34. BALANUS ALLIUM. Pl. 7, fig. 7 _a_-7 _d_. _Shell faintly tinged with purple: radii broad, with their summits not oblique: basis not porose. Scutum with the lines of growth crenated: tergum with the spur extremely short, truncated, broad as half the valve._
_Hab._--Raine's Islet, Barrier Reef, Australia, Mus. Stutchbury. Hab. unknown, attached to and coated by Porites. Mus. Brit. _General Appearance._--Shell conical, smooth, but with the lower part sometimes narrowly ribbed in lines corresponding with the internal longitudinal ribs; tinted pale peach-blossom purple, owing to the sheath being finely so coloured; or wholly white. Radii broad, white, square on the summit, hence orifice entire, ovate passing into rhomboidal. The parietal portion of the carino-lateral compartments extremely narrow, about one eighth of the width of the parietes of the lateral compartments. Basis concave, partially imbedded in the coral. Largest specimen .35 of an inch in diameter. There are some specimens in Mr. Cuming's collection which appear to belong to this species, and are certainly very closely allied to it, but not having the opercula, cannot be identified positively; the shell is flatter, with the walls strongly ribbed up to the orifice, which is more rhomboidal: the basis is much more cup-formed and more deeply imbedded in the coral; but these differences by themselves are by no means sufficiently diagnostic.
_Scutum_: the lines of growth are crenated, causing the surface to be very obscurely striated longitudinally: the articular ridge is very prominent, as can be best seen from the outside, and runs down the whole length of the tergal margin with a very regular curve, and hence differs from the articular ridge in the foregoing species. The adductor ridge is either absent, or very indistinct, and parallel to the articular ridge: there is a deep little pit for the lateral depressor muscle. _Tergum_ (7 _d_), with the apex somewhat produced or beaked, and tinged purple: external surface almost flat, without any longitudinal furrow: scutal margin curved. Spur very short, placed quite close to the basi-scutal angle of the valve; broad as half the valve; lower end square. Internally, the articular ridge is prominent only in the uppermost part of the valve: crests for the depressores very feeble. _Parietes_: their internal surface is very strongly ribbed longitudinally, the ribs being coarsely denticulated at their bases, and finely fluted along their sides. The sheath is transversely ribbed, and clothed with an epidermis furnished with transverse rows of fine hairs. The _radii_ are of a dead white, whereas the parietes are translucent; the summits are parallel to the basis; they are broad; the radii of the carino-lateral compartments appear extraordinarily broad, owing to the narrowness of the parietal portion: the sutural edges are furnished with coarse septa, which are sinuous, irregular, and obtusely denticulated; the interspaces are filled up solidly. The _alæ_ are thin, with their sutural edges almost smooth, and their summits oblique: in some specimens, during the diametric growth, a mere, almost thread-like ribbon is added to their sutural edges. _Basis_ slightly cup or saucer-shaped; moderately thick, permeated by fine pores, and generally ribbed in lines radiating from the centre. The walls and basis adhere together very firmly.
_Mouth_: labrum with six teeth: mandibles with five teeth; the three upper teeth being sharp, narrow, and unusually prominent; the two lower teeth minute and sharp; maxillæ without a notch. _Cirri_ much injured: first pair with one ramus apparently one third longer than the other: segments not very protuberant: the posterior cirri have elongated segments with five pairs of spines. _Affinities._--This species is very distinct from all the foregoing: in the carino-lateral compartments being so narrow, and tending, as we may suppose, to become aborted; in the form and structure of the whole shell, and in its habits, this species shows an affinity and passage to the coral-inhabiting sub-genus Creusia, which has only four compartments. There is also a close affinity to the sub-genus Acasta. This species is so closely allied to the following, that I at one time felt some doubts whether they ought to have been specifically separated; it is also probably closely allied to _B. terebratus_, but the materials hardly suffice for judgment: it is also related, though less obviously, to _B. vestitus_. 35. BALANUS CEPA. Pl. 7 fig. 8 _a_-8 _c_. _Shell dirty reddish-purple, steeply conical: radii narrow: basis obscurely porose. Scutum with the lines of growth crenated: tergum with the spur truncated, broad as half the valve, and depending beneath the basi-scutal angle as much as half its own breadth._
_Hab._--Japan, attached to an Isis, Mus. Cuming. Attached to an oyster, Mus. Stutchbury. As already stated, this species comes in all essential respects very near to the last, though differing much in appearance; I have seen two sets of specimens, and two sets of _B. allium_, and there was no variability or passage in the points in which they differed; hence I must consider them as specifically distinct. _Shell_, steeply conical, strongly but bluntly ribbed longitudinally; coloured either all over dull reddish purple, or with the upper part only pinkish purple: in one set of specimens, the yellow epidermis was partially persistent. Radii narrow. Orifice small, ovate. The wall of the carino-lateral compartment is very narrow. The internal surface of the parietes is ribbed, but finely, and only in the lower part. The septa, on the sutural edges of the radii, are finer than in _B. allium_. Basis flat, obscurely permeated by pores. The largest specimen is .25 of an inch in basal diameter. _Scuta_: these are longitudinally and finely striated; the basi-tergal corner is more rounded off than in _B. allium_, and the articular ridge is not nearly so prominent: internally, the adductor ridge is rather more prominent. The _Tergum_ is rather broader: its apex is produced into a minute sharp point: the scutal margin is straight; the spur is broader, and measured from the basi-scutal angle of the valve, considerably longer; namely, as long as half the width of the basal margin of the spur, whereas in _B. allium_ it is only about a quarter as long as the basal margin of the spur: the lower edge of the spur is not here so directly transverse to the longitudinal axis of the valve as in _B. allium_: the external surface is not so flat as in that species, and a depression runs down to the basi-scutal angle of the spur.
Considering the difference in the shape and appearance of the shell, with its narrow radii and small orifice; considering the less strongly ribbed internal lamina of the parietes, the finer septa on the sutural edges of the radii, the slight difference in outline in the scuta and terga, more especially the greater length of the spur, I conceive I am right in ranking this form as a distinct species, though assuredly it is very closely allied to _B. allium_, and even still closer to the following _B. quadrivittatus_. 36. BALANUS QUADRIVITTATUS. Pl. 8, fig. 1. _Shell steeply conical, having four longitudinal gray bands placed crosswise: radii with their summits oblique: basis thin, solid. Scutum, with the lines of growth smooth; no distinct pit for the lateral depressor muscle: tergum as in B. cepa._ _Hab._--East Indian Archipelago, attached to lamelliferous corals, and associated with _Pyrgoma grande_ and _Creusia spinulosa_, Mus. Brit. and Stutchbury and Darwin. Philippine Archipelago, attached to a Tetraclita, Mus. Cuming. I have seen four sets of specimens of this species, taken in four different places, one set containing above twenty individuals, and all resembled each other exactly: nevertheless, this species comes so close to _B. cepa_, that I am somewhat doubtful about its specific distinctness.
_General Appearance._--Shell smooth, or slightly folded, steeply conical; white, with four longitudinal bands of pale brownish-gray colour, namely, on the rostrum, the carina, and the two lateral compartments: the carino-lateral compartments are very narrow and almost white: the four brownish-gray bands are darkest in the upper part of the shell, though always rather faint, and die out towards the base: they can sometimes be seen to be formed of several narrow longitudinal stripes; the tint shows a trace of containing purple. The orifice of the shell is small, rhomboidal, and not quite entire, owing to the obliquity of the summits of the moderately broad radii. In structure, the shell, radii, and alæ resemble those in the last species. The basis, however, does not appear to be permeated by pores. Basal diameter of largest specimen .25 of an inch. The _Scuta_ most closely resemble those of _B. cepa_, but the lines of growth are not crenated, and internally there is only a very minute pit for the lateral depressor muscle, placed almost on the edge itself of the valve. The _Tergum_ hardly differs at all from that of _B. cepa_, but is perhaps of rather greater breadth. The _Mouth_ does not differ from that in the last two species. In the _Cirri_, the three posterior pairs have elongated segments, bearing only three pairs of spines, of which the lowest pair is minute: in _B. allium_, and I believe in _B. cepa_, there are five pairs of spines on each segment.
This species differs from the last only in the peculiar colouring, smoother walls, more oblique radii, solid basis, and more especially in the scuta having the lines of growth not crenated, and internally, in the pit for the lateral depressor muscle being so very minute and placed on the basi-tergal edge of the valve. The posterior cirri, also, I believe, differ in the number of the spines which the segments support; nevertheless, I cannot feel confident about the specific distinctness of _B. quadrivittatus_. 37. BALANUS TEREBRATUS. Pl. 8, fig. 2 _a_-2 _b_. _Shell white, strongly ribbed longitudinally, with the basal margin produced into long points: basis concave, not permeated by pores, but strongly ribbed externally in radiating lines; the interspaces between the ribs being riddled by minute rounded apertures, often placed in double rows._ _Hab._--Unknown, Brit. Mus., attached to a lamelliferous coral. I have in this instance broken through my rule of not describing a Cirripede without examining the opercular valves; but the species here named is so peculiar, that it would have been a fault to have passed it over. There is but a single specimen in the British Museum, without, as just stated, the operculum, and of course without the animal's body. _Shell_, white, depressed, conical, somewhat elongated in its rostro-carinal axis; orifice rather small, pentagonal, toothed, elongated. Parietes rather thin, with extremely prominent longitudinal ribs, produced at the basal edge into long spikes: the internal surface is also ribbed, but less strongly than the outside. Radii rather narrow, with oblique, not smooth summits; sutural edges very finely and obscurely crenated. Alæ with their summits extremely oblique. Lower edge of sheath closely attached to the walls. The carino-lateral compartments are rather narrow.
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