A Monograph on the Sub-class Cirripedia · Charles Darwin
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_Animal's body_ unknown. 11. BALANUS GALEATUS. Pl. 3, fig. 4 _a_-4 _c_. LEPAS GALEATA (?) _Linnæus._ Mantissa altera Holmiæ, 1771. CONOPEA ELONGATA. _Say._[90] Journal of Acad. Nat. Sci. Philadelphia, vol. ii, part 2, p. 323, 1822. [90] If I have assigned the specific title of _galeatus_ to the wrong species, yet Say's name of _elongatus_ ought not strictly to be admitted; as the _Lepas elongata_ of Gmelin is a Balanus,--probably a variety of _Balanus crenatus_. I may add, that as the _Lepas galeata_ of Schröter ('Einleitung in die Conch.' &c.), was attached to a Gorgonia from the East Indies, it cannot be our present species, but probably is one of the three other allied species, which all occur in India. _Parietes not porose; basis porose. Tergum, with the apex square, caused by the great development of the articular ridge._ _Hab._--Charlestown, South Carolina; Florida; West Indies; Central America; attached to Gorgoniæ; Mus. Brit., Agassiz, Cuming, Stutchbury.
_General Appearance._--This and the two following species come so close in general appearance to the last, that it will be quite superfluous to do more than describe the few points of difference. The shell and basis are generally quite as much elongated as in the last species, and sometimes much more so, owing to the carinal end (fig. 4 _a_), with the corresponding portion of the basal cup, being produced like the rostral end, into a flattened, sharp point: I have seen a specimen in this state .9 of an inch in length, and only .25 in breadth in the broadest part. In many specimens, however, the shape is exactly as in _B. calceolus_; but the rostrum seems less usually furrowed from clasping the stem of the Gorgonia. The colour is paler, pinker, and more distinctly striped longitudinally than in _B. calceolus_; I have, however, seen some not-striped, purple specimens (and one transversely freckled with white) from the West Indies. The parietes are strongly-ribbed internally, and are not permeated by pores. The radii have their sutural edges crenated. The basal cup is permeated by pores. The _Scutum_ differs from that in the last species, only in the pit for the lateral depressor muscle, being much shallower, and less defined, and in the apex being truncated. The _Tergum_ is remarkable from its broad, square, truncated summit, which underlies the whole broad apex of the scutum: the square summit of the tergum is formed by a great and peculiar development of the uppermost part of the articular ridge. The spur is a little narrower than in _B. calceolus_.
_Mouth_: on the crest of the labrum there are two teeth on each side of the central notch. The mandibles have five teeth, of which the two lower are very small. The maxillæ show a trace of a notch under the upper large pair of spines; near the inferior angle there are two long spines. _Cirri_: in the first pair, one ramus is nearly twice as long as the other: the segments are not very protuberant. There is a sharp point at the dorsal basis of the penis. The branchiæ are of moderate size, and plicated on one side. 12. BALANUS CYMBIFORMIS. Pl. 3, fig. 5 _a_, 5 _b_. _Parietes and basis not porose. Scutum and Tergum with very small articular ridges. Tergum broad, almost equilateral._ _Hab._--Attached to a Gorgonia, Tubicoreen, near Madras, (Dr. Johnston). Hab. unknown, Mus. Cuming. _General Appearance._--I have seen only two specimens, kindly sent me by Dr. Johnston, and a single specimen in Mr. Cuming's collection. In most points this species agrees with the two last species. The shell (excepting the rostrum), and even the opercular valves in Mr. Cuming's specimen were of a very fine purplish-red; in the other specimens they were feebly tinted purple. The parietes are strongly ribbed internally, and are not permeated by pores. The basal cup is not porose, but its inner surface is ribbed in lines radiating from the centre, and in both these respects this species differs from the two foregoing. The Radii are rather narrow; they are paler coloured than the parietes; they have their sutural edges plainly crenated. The alæ have extremely oblique summits; the narrow rim added during the diametric growth of the shell is white, the rest of the sheath being, in Mr. Cuming's specimen, finely coloured like the parietes. Basal diameter of the longer axis of the largest specimen, .4 of an inch.
_Scutum_, rather narrow, with the basi-tergal corner much rounded off; externally the lines of growth are little prominent. Internally, the articular ridge is extremely little developed, and not at all reflexed; there is no adductor ridge; there is a minute pit for the lateral depressor muscle, placed almost on the edge of the valve. The _Tergum_ is broad, forming (the spur being excepted) an almost equilateral triangle. The articular ridge is remarkably little prominent, and placed close to the scutal margin. The spur is nearly half as broad as the valve, with its extremity or basal margin in one case obliquely truncated, and in another case nearly square. _Animal's body_ unknown. 13. BALANUS NAVICULA. Pl. 3, fig. 6 _a_-6 _d_. _Parietes and basis not porose: carino-lateral compartments very narrow, and of nearly the same width from top to bottom: radii with their sutural edges smooth. Scutum externally striated longitudinally._ _Hab._--Attached to Gorgoniæ, Tubicoreen, Madras (associated with _B. calceolus_), Dr. Johnston. Hab. unknown, Mus. Brit. and Darwin. This is a very distinct form, though nearer to the foregoing than to the other species. Its separation from the sub-genus Acasta is quite artificial; its affinity to this sub-genus is shown by its weaker shell, non-porose parietes and basis; by the radii having their sutural edges smooth, and their summits not quite square; by the carino-lateral compartments being very narrow; by the less elongated basis, not furrowed, from not clasping the branches of the Gorgonia; and by the longitudinally striated scuta; nevertheless, from the similar habits, and from the graduated structure in the five foregoing species, it cannot be removed out of the genus Balanus. I have seen three sets of specimens of this species.
_General Appearance._--Shell, sometimes with the rostrum, and sometimes with the carina, and corresponding portions of the basal cup, elongated; but not, apparently, to so great a degree as in the foregoing species; basis not furrowed, from not clasping the branches of the Gorgonia. Colour pale blueish-purple, with the radii whiter. The surface is studded with small calcareous points. The carino-lateral compartments are very narrow, not more than one tenth of the width of the lateral compartments; they are, moreover, scarcely wider at the base than at the summit. The summits of the radii are, apparently, a little oblique, or at least not so square as in the foregoing species. The shell is not nearly so strong as in the last three species; and the compartments separate by gentle force, and from the action of caustic potash. The largest specimen was .4 of an inch in basal diameter. Internally, the parietes are not very strongly ribbed, or they are almost smooth, and there are no pores. The basis is concave and smooth within, and is not porose. The sutural edges of the radii are quite smooth, or sometimes they exhibit, in the lower part, mere traces of septa,--a character by itself sufficient to separate this from the foregoing species. The alæ have oblique summits, and the rather narrow portion added during the diametric growth of the shell, is white.
The _Scutum_, externally (6 _d_), has raised striæ, radiating from the apex; valve rather thick; internally, the articular ridge is but slightly prominent, and its lower end is rounded off: the depression for the lateral depressor muscle is slight; between this depression and that for the adductor muscle, the surface of the valve is prominent. _Tergum_, somewhat beaked; externally, the surface is depressed in the line of the spur: the carino-basal margin slopes towards the spur. _Animal's body_ unknown. _Section_ C. _Parietes and basis permeated by pores. Radii not permeated by pores._ 14. BALANUS TRIGONUS. Pl. 3, fig. 7 _a_-7 _f_. _Parietes ribbed, mottled purplish-red; orifice broad, trigonal, hardly toothed. Scutum thick, with from one to six longitudinal rows of little pits. Tergum without a longitudinal furrow; spur truncated, fully one third of width of valve._ _Hab._--Java; East-Indian Archipelago; Peru; West Columbia; California; Sydney; New Zealand. Mus. Brit., Cuming, Stutchbury, Dunker, &c. _General Appearance._--Shell conical, generally depressed; orifice broad, triangular, almost equilateral; walls coloured or only mottled with purplish-pink, having either irregularly branching, or regular, longitudinal ribs, which are generally white. The radii are pale pink, or nearly white: the opercular valves have either their upper parts, or nearly their whole surface, clouded with pinkish-purple: the epidermis is not persistent: the walls are moderately strong: the largest specimen was one inch, but generally full-grown specimens are about half an inch in basal diameter.
The _Scuta_ have the lines of growth highly prominent. From one to five or six rows (7 _b_, 7 _c_) of nearly circular, or transversely oblong, deep pits, extend down the middle of the valve; rarely there is not even one row; in this latter case, the valve is not striated longitudinally. These little pits are caused by one or more deep longitudinal furrows, crossed by the lines, or rather ridges, of growth. In the same group of specimens, I have seen individuals with three, five, and six rows; and even a few specimens with only one row, or none at all. The outline of the valve is elongated, with the apex slightly reflexed: the inner surface is protuberant, sometimes to a remarkable, but variable degree. The articular ridge is not very prominent, but it extends fully half-way down the valve, and generally ends in a small free point. There is a short adductor ridge, and a deep narrow pit or cleft for the lateral-depressor muscle. _Terga_, externally smooth, flat, with scarcely a trace of a longitudinal furrow; spur broad (7 _e_, 7 _f_), varying from half to one third of the width of the valve, with the end truncated, situated either near or quite close to the basi-scutal angle. The crests for the depressor muscles are moderately well developed.
_Compartments._--The parietal tubes are, in their upper parts, filled up solidly, without transverse septa. The radii generally have their summits slightly oblique, and this is almost always the case with the radii of the rostrum; the other radii sometimes extend from tip to tip of the parietes, and are parallel to the basis; rarely the radii are considerably oblique. The septa of the radii are very obscurely denticulated, and the interspaces between them are filled up solidly. The alæ have their sutural edges thin and smooth. _Mouth._--Labrum with three teeth close together on each side of the central notch: mandibles with four teeth, the fourth being small, the fifth either absent or scarcely distinguishable from the inferior angle: maxillæ without any notch, with the two lower spines rather longer than the others. _Cirri_: In the first pair, one ramus is only half the length of the other; in the second pair, both rami are short and about equal in length; in the posterior pairs, the segments, which are not protuberant, bear four pairs of spines, of which the three lower pairs are short. This species is widely-distributed, and where found seems to be common. It is generally attached to shells of mollusca, but I have seen it also attached to wood. I have found it associated with _B. tintinnabulum, var. concinnus_, and _coccopoma_, with _B. psittacus_, _improvisus_ and _amphitrite_, and with _Elminius modestus_.
Young specimens bear a considerable resemblance to certain young varieties of _B. tintinnabulum_, and can indeed be distinguished from them only by a careful examination of the opercular valves; for it should be borne in mind, that in certain cases the scuta in _B. tintinnabulum_ are pitted with little cavities. This species in some respects is, I think, allied to _B. porcatus_, but it is far more closely related to _B. spongicola_, and can be discriminated with difficulty from certain varieties of this latter species. In Mr. Cuming's collection, there is a group of small specimens, crowded between some older specimens, which are remarkable from the shell being oval in a transverse section,--from the smoothness of the walls,--and from the absence of pits on the scuta; yet there could be no doubt that these specimens belonged to our present species. 15. BALANUS SPONGICOLA. Pl. 4, fig. 1 _a_-1 _d_. BALANUS SPONGICOLA. _Brown's_ Illustrations of the Conchology of Great Britain (1827), pl. 7, fig. 6: 2d edit. (1844), pl. 53, figs. 14-16. _Parietes generally smooth, sometimes longitudinally folded; coloured pink: orifice toothed. Scutum longitudinally striated. Tergum, with the apex produced, without a longitudinal furrow; spur truncated, about one third of width of valve._ _Var. with the walls slightly folded longitudinally._ _Hab._--South coast of England, and Tenby in South Wales, often imbedded in sponges; attached also to shells and rocks in deep water; Mus. Brit., Jeffreys. Algiers, on Mytili and Serpulæ, with _B. perforatus_, Mus. Mac Andrew. Madeira, with _B. tulipiformis_, Mus. Lowe. Lagulhas Bank, Cape of Good Hope, on detached kelp, with _B. Capensis_, Mus. Sir J. Ross. Imbedded in sponge with _Acasta spongites_, Mus. Bowerbank. _Var._ West Indies.
_Fossil_ in Coralline Crag, Mus. S. Wood. _General Description._--Shell tubulo-conical; orifice of moderate size, rather deeply toothed; colour dull pink, or purplish, or dark flesh-colour; sometimes the radii are paler, sometimes of the same colour with the parietes. Surface smooth when well preserved, having transverse rows of minute spines. In the West Indian variety the walls are slightly or much folded, but I will describe this form separately. Size of largest specimen (Mus. Jeffreys), .6 of an inch in basal diameter. _Scutum_, with fine ridges radiating from the apex, and with the lines of growth, crenated: internally, the articular ridge is small, adductor ridge short and barely distinct: there is a rather deep and narrow pit for the lateral depressor muscle. The whole valve is much thinner than in _B. trigonus_, which in most respects it closely resembles. _Tergum_, with the apex pinkish purple, produced or beaked, but the beak is not needle-like, as in _B. psittacus_ and its allies, for the carinal margin is perfectly preserved up to the tip. Externally the valve is nearly flat, for the longitudinal furrow is very shallow. The spur is about one third of the width of the valve; its lower end is abruptly truncated: in European specimens (1 _b_) the whole basal margin, on the carinal side, slopes down to the spur in a straight line, which, together with the sharpness and production of the basi-scutal angle of the spur itself, gives to the whole valve a peculiar appearance: in the specimen (1 _c_) from the Lagulhas Bank, the basal margin on the carinal side is a little more hollowed out, but it is quite impossible to doubt about the specific identity of these specimens: in the West Indian variety (1 _d_) the basal margin on the carinal side forms a distinct but obtuse angle with the spur. In all cases the crests for the depressor muscles are very feebly developed.
The _Compartments_ have their radii developed to a rather varying degree, with their summits oblique; hence the orifice is toothed: the sutural edges of the radii have their septa barely denticulated; the sutural edges of the alæ are smooth. The basis, as with the other species of this section, is permeated by pores; yet I found one specimen, from the Cape of Good Hope, with the basis apparently solid, thus offering a very singular anomaly. In the specimen imbedded in sponge, the basis, as viewed externally, is concave; whereas in Acasta, which always inhabits sponges, the basis is highly convex or hemispherical. The _Mouth_ and _Cirri_ resemble those of _B. trigonus_, and I can point out no distinguishing character. With respect to the variety from the West Indies, I have seen two sets of specimens differing somewhat in external appearance, one set attached to a coral from St. Vincent's, and another set to an Avicula from an unknown locality; at first I described these specimens, with some hesitation, as a distinct species, and I am very far from sure whether this would not have been the more correct course, although I am unable to point out any sufficient diagnostic characters. This form differs from the ordinary _B. spongicola_, in the walls being more rugged, stronger, and slightly or deeply folded longitudinally; in this latter case the shell in external aspect differs much from ordinary specimens of _B. spongicola_; but this is a variation so common that I dare not place any reliance on it. The colour is more purple; the summits of the radii perhaps rather less oblique. In the scuta the only difference is that the articular ridge seems rather longer, and the adductor ridge perhaps more prominent: in the terga, as already remarked, the basal margin on the carinal side does not slope so straight into the spur. These differences I consider all too slight to be of specific value. The difficulty in determining the nature of this variety is added to by its approach to _B. trigonus_ in all those points in which it departs from the ordinary _B. spongicola_, so that for a short time I was even tempted to consider both these species as varieties of one form. But until _B. trigonus_ is found with its scutum longitudinally striated, and with its tergum beaked, it can hardly be confounded with _B. spongicola_; for it should be observed that when in _B. trigonus_ the rows of little pits disappear from the scuta, as sometimes happens, though rarely, yet these valves do not become longitudinally striated.
_Balanus spongicola_ occurs, mingled with _B. tulipiformis_, in the Mediterranean, and by the external characters of the shell alone cannot be distinguished from that species; but the striated scuta and beaked terga suffice to separate them. Again, this species, at the Cape of Good Hope, occurs mingled with _B. Capensis_, and from the non-striped young varieties of that species, it can, externally, be distinguished only by the beak of the tergum not being sharp like a needle. I have seen a single, perfectly characterised specimen, with its opercular valves preserved, found by Mr. S. Wood in the Coralline Crag at Sutton, mingled with _B. inclusus_. 16. BALANUS LÆVIS. Pl. 4, fig. 2-2 _g_. BALANUS LÆVIS. _Bruguière._ Encyclop. Meth. (1789), Pl. 164, fig. 1.[91] ---- DISCORS. _Ranzani._ Mem. di Storia Nat., 1820, Tab. 3, figs. 9 to 13. ---- COQUIMBENSIS. _G. B. Sowerby_, in Darwin's Geology of South America (1846), Tab. 11, fig. 7. [91] M. Deshayes, in his descriptions of the plates, considers this figure, I have no doubt erroneously, as that of _B. perforatus_, of Bruguière. The _B. Coquimbensis_ of Sowerby, is a different species from the _B. Coquimbensis_, of Chenu, 'Illust. Conch.,' tab. 6, which latter is unknown to me. _Shell covered by brown membrane, or naked and white or pale purple; orifice small; radii very narrow. Scutum with one or two deep longitudinal furrows._
_Var._ nitidus (fig. 2): _shell not covered by membrane, white or pale purple: orifice but slightly toothed: scutum generally with two furrows_. Hab.--Chile, as far south as Concepcion; Peru; California. _Var._ Coquimbensis (fig. 2 _a_): _with the basal cup partly filled up with thin, irregular, calcareous layers, making a cancellated mass_. Fossil, and recent. _Hab._--Strait of Magellan, ten to twenty fathoms, attached to shells; often entirely surrounding pebbles, forming globular masses; associated with _Verruca lævigata_. Chile and Peru, (generally _var. nitidus_), often attached to _Balanus psittacus_. California. Very common. _Fossil_ in an ancient tertiary formation (middle bed) at Coquimbo, Chile. In a recent deposit (_var. nitidus_) at the height of 1000 feet at Valparaiso; with Human remains at San Lorenzo, Callao, Peru.
I may premise that, having myself collected this species from the same locality, the Strait of Magellan, where no allied species occurs, attached to the same Mytilus and associated with the same Verruca, I feel confident that it is the _B. lævis_ described by Bruguière; and there can hardly be any doubt that it is the _B. discors_ of Ranzani. With respect to the old tertiary specimens from Coquimbo, named _B. Coquimbensis_ by Sowerby, they differ from the recent in no respect, except in being considerably larger; and therefore I cannot consider them specifically distinct. At first I was unwilling to believe that the specimens with a single very broad longitudinal furrow, and those with two rather broad, or with one narrow furrow, on their scuta, could belong to the same species; but I soon found that all these varieties occurred mingled together, and that they differed in no other respect whatever. Generally, however, all the individuals in the same cluster had the same variety of scutum,--thus adding one more to the many instances amongst cirripedes of variations common to whole groups of specimens. Still more unwilling was I to believe that _var. nitidus_ and the common variety could belong to the same species.
Their general aspect is totally unlike: _var. nitidus_ has a smooth, clean, naked shell, either white or pale purple, somewhat globulo-conical, often with a nearly entire orifice; whereas the other common variety generally has a more steeply conical shell, with a toothed orifice, and is covered by a dirty brownish membrane. Moreover, though I have seen hundreds of specimens from Tierra del Fuego, I have not seen one specimen of _var. nitidus_, or even of an approach to it in appearance; and, on the other hand, _var. nitidus_ is the common form in Chile and Peru; though I have seen one or two specimens of the membrane-covered variety from Valparaiso. Such facts strongly induced me to believe that these forms were specifically distinct; but upon careful examination I could find no other or more important differences than those just specified. Some specimens from northern Chile are in an intermediate condition; and from Concepcion, in the south of Chile, where the climate approaches in character to that of the more southern parts of the Continent, there are many specimens, in so intermediate a condition that I know not whether or no to rank them under _var. nitidus_. Thus I became convinced that these forms are only varieties. At Concepcion, some few specimens are pale purple, and yet are wholly invested by thick brown membrane, thus uniting the two extreme varieties. From California I have seen both varieties, but I do not know which is most common there. With respect to the great difference in aspect between the specimens from northern Chile and Tierra del Fuego, we shall hereafter see a strictly analogous case in _Balanus flosculus_. Finally, I may add that _B. lævis_ seems to represent in the southern hemisphere and on the west coast of North America, the _B. perforatus_ of Europe and Western Africa.
_General Appearance._--Shell conical, sometimes slightly globular; surface smooth (that is, not folded), either naked, and in that case white or pale purple, or covered by dirty yellowish-brown membrane. Orifice small, more or less toothed, rarely exceeding one third of the basal diameter. Radii very narrow, often not developed, the six sutures forming in all cases deep and narrow clefts. The largest recent, but much depressed, specimen which I have seen (from the Strait of Magellan) was three fourths of an inch in basal diameter; specimens growing congregated are often much elongated. I have seen one with the basal cup between two and three times as deep as the height of the compartments. Of the ancient tertiary specimens, the largest had a diameter of three fourths of an inch, and a total length of actually two inches (fig. 2 _a_); another of these fossils had a basal cup in depth equalling four fifths of the entire length of the shell and basis. The _scutum_ has either one very broad and deep longitudinal furrow (2 _b_), or two moderately broad and deep (2 _e_), or two narrow and deep, or less frequently one narrow and inconspicuous longitudinal furrow (2 _f_); rarely there is not one furrow; sometimes there are none towards the apex, whilst furrows have been formed in the lower part of the valve. In young specimens the furrows extend down to the actual basal margin, but in old specimens they often fall short of this, and, as a consequence, the furrows become crossed by one, two, or three calcareous ridges, which ridges at successive periods formed the basal margin of the valve. The external surface is covered by yellow membrane; and fragments of several successive opercular membranes are often attached to the zones of growth.
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