A Monograph on the Sub-class Cirripedia · Charles Darwin
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_Basis_ thin, porose; sometimes with an underlaying cancellated layer. _Mouth_: labrum with six teeth: mandibles with the fourth and fifth teeth small, either sharp, or blunt: maxillæ with a straight edge, or with the inferior part slightly prominent. _Cirri_ with the rami of the first pair unequal by four or five segments: the segments in the shorter ramus are extremely protuberant. The segments in the second cirrus only moderately protuberant: but all the specimens were in bad condition, and it appeared as if, in the Panama specimens, the segments of the second cirrus were more protuberant than in the Philippine Island specimens. In the posterior cirri there are from three to five pairs of spines on each segment: even amongst the Panama specimens some had three and some four pairs, and a white Panama specimen had five pairs of spines. All the recent specimens which I have seen, were, with one exception, attached to various shells and crabs, and to each other. The Peruvian specimen was associated with _B. flosculus_. The tertiary specimens are often congregated together into great masses. Including the recent and fossil specimens, this species encircles the globe. During the miocene period it seems to have been the commonest existing sessile cirripede; now, it does not appear to be common, excepting, perhaps, at Panama: Mr. Cuming procured only one specimen from the Philippine archipelago.
19. BALANUS AMPHITRITE. Pl. 5, fig. 2 _a_-2 _o_. LEPAS RADIATA. _Wood's_ General Conchology (1815), Pl. 7, fig. 7. ---- MINOR? _Wood's_ General Conchology (1815), Pl. 7, fig. 6. ---- BALANOIDES. _Poli._ Testacea utriusque Siciliæ (1795), Tab. 5. BALANUS BALANOIDES. _Risso._ Hist. Nat. de l'Europe Merid., tom. iv, 1826. _Shell longitudinally striped with purple or pink; sometimes with the stripes confluent; sometimes wholly white. Scutum internally with a prominent broad adductor ridge._ _Var._ (1) communis: (2 _e_, 2 _h_, 2 _l_,) _nearly white, with pale or dark violet-coloured longitudinal stripes: epidermis rarely persistent: shell either thin or thick: radii white or freckled with reddish mahogany colour, with their summits either oblique, sometimes in a high degree, or nearly parallel to the basis: basal point of spur of the tergum either square or bluntly pointed_. Hab. Mediterranean, W. Indies, S. Africa, Philippine Archipelago, New South Wales. _Var._ (2) venustus: (2 _a_,) _white or pale pink, with narrow bright pink, or broad pinkish-purple stripes; orifice either much dentated or nearly entire. Tergum with the carinal half of the basal margin sometimes much hollowed out_. Hab. W. and S. Africa, Ceylon. _Var._ (3) pallidus: (2 _c_, 2 _k_,) _white, with or without a yellowish persistent epidermis; sometimes with the edges of the compartments tinted purple: radii moderately oblique: tergum generally narrow, with the spur sharp, and the basal margin on its carinal side much hollowed out_. Hab. W. Africa, Madagascar, Red Sea.
_Var._ (4) niveus: (2 _f_,) _white, with longitudinal hyaline lines; epidermis not persistent_. Hab. W. Indies, Florida, S. Africa, &c. _Var._ (5) modestus: _upper part of shell white, lower part uniform blueish-gray, opercular valves as in_ Var. (1). Hab. unknown. _Var._ (6) Stutsburi: (2 _d_, 2 _i_, 2 _m_, 2 _n_, 2 _o_,) _white, with or without pinkish-purple stripes, which are often confluent, rendering the lower part of the shell of a uniform purplish tint; epidermis persistent: radii very narrow: tergum narrow, spur sharp, varying in form and in exact position; carinal margin sometimes highly protuberant; basal margin on the carinal side of the spur generally, but not invariably, much hollowed out_. Hab. West Africa. _Var._ (7) obscurus: (Pl. 5, fig. 2 _g_,) _with narrow, approximate, obscure and often almost confluent, slaty, or pale purplish-brown, or dark slate-coloured stripes_. Hab. West Indies, Australia, and unknown. _Var._ (8) variegatus: _with narrow, approximate, dusky, claret-coloured stripes, transversely freckled with white; shell conical; walls very thin: scutum with the adductor ridge small_. Hab. New Zealand. _Var._ (9) (_an. spec._?) cirratus: (fig. 2 _b_,) _shell very pale purplish-brown, with faint, more or less plain longitudinal stripes, transversely freckled with white; walls thin: scuta with the lines of growth beaded: basis, in specimens growing in groups, irregularly cup formed: maxillæ with the inferior corner extremely prominent_. Hab. Mouth of Indus, Australia, Philippine Archipelago.
_Hab._--Warmer temperate and tropical seas; extremely common; Mediterranean, Smyrna, Sicily, Coast of Portugal; West Coast of Africa, River Gambia, West Indies, Demerara, Natal, Madagascar, Red Sea, Mouth of the Indus, Ceylon, Philippine Archipelago, East Indian Archipelago, Pacific Ocean, east coast of Australia, New Zealand; extremely common on ships' bottoms; often attached to floating timber, canes, &c.; often associated with _B. tintinnabulum_; attached to pebbles and various shells. With respect to the nomenclature of this extremely common species, which is widely distributed in all the warmer seas (excepting, as far as I have seen, on the west coast of America), there is some difficulty. I have no doubt that it is the _Lepas radiata_ of Wood (1815), but Bruguière, in 1789, gave this same name to a Balanus which he had not seen, but which is figured in Chemnitz, Tab. 59, fig. 842. I should have thought that this also had been the present species, but Spengler, in describing (Skrifter af Naturhist. Selskabet i, B. 1790) this individual specimen, which he calls _L. purpurea_, states that it is 13 lines in basal diameter; now this is a size which is never acquired by _B. amphitrite_; and the description, habits, and size, would apply equally well to the species which I have called _B. amaryllis_; but when no notice is taken of such points of importance, as whether the walls are permeated by pores, whether the radii are smooth-edged, whether the scuta are striated, it is impossible to identify with any approach to certainty sessile Cirripedes; and the names given ought, in my opinion, to carry little weight with them. With respect to Lamarck's _Balanus radiatus_ (1818), the synonyms quoted exhibit some great and inextricable confusion. The _B. radiatus_, again, of Risso, is a fossil and apparently distinct species. There can be no doubt that the present species is the _Lepas balanoides_ of Poli, (and of several authors who have followed him), and equally little doubt that the present species is not the true _L. balanoides_ of Linnæus, which has a membranous basis, and which I have not seen from the Mediterranean. Under these circumstances I have concluded that less confusion would be caused by giving a new name to this species than by taking that of Wood, which ought not to have been used by him, considering Bruguière's previous adoption of it.
Under the head of _B. tintinnabulum_ I have alluded to the great variation of _B. amphitrite_, which consists not only in a vast diversity in the colouring and in the general aspect, but likewise in the degree of obliquity of the summits of the radii, in the form of the terga, and slightly in that of the scuta. In order to show that it has not been from indolence that I have put so many forms together, I may state that I had already named and fully described in detail eight of the following forms as species, when I became finally convinced that they were only varieties: it would require at least thirty figures, which I have not the power to give, fully to illustrate the transitional forms. As with _B. tintinnabulum_, the deception is wonderfully enhanced by whole groups of specimens from the same locality exactly resembling each other, and sometimes differing from other groups attached to the very same object.
If a person were to get together only some fifty or sixty specimens from only half a dozen different localities, he would almost certainly come to the same conclusion, as I at first did, that several of the varieties are true species; but when he gets several hundred specimens from all quarters of the globe, he will find, to his trouble and vexation, that character after character fails and blends away by insensible degrees, and he will be led, as the more prudent course, to include, as I have done, and I hope rightly, all under one specific name. I have experienced more doubt regarding the last variety, _cirratus_, than on any other, on account of its peculiar colouring, and from the basis being often irregularly cup-formed. Under _B. concavus_ I have remarked how closely some of its varieties approach to _B. amphitrite_, and it is to this last variety that they approach; almost the only difference being that the scuta in _B. concavus_ are longitudinally striated. Yet some of the varieties of the two species are so distinct that it would be puerile to class them together. I will only add, that after studying such varying forms as _B. tintinnabulum_ and _amphitrite_ it is difficult to avoid, in utter despair, doubting whether there be such a thing as a distinct species, or at least more than half a dozen distinct species, in the whole genus Balanus.
As with _B. tintinnabulum_, I will first give a full description of the more common forms, alluding only to each less frequent variation, and then separately describe briefly the more marked varieties. _General Appearance._--Shape conical, either steep or considerably depressed; sometimes tubular; orifice either nearly entire or deeply toothed, not large, varying from rhomboidal to rounded-trigonal. Surface of shell smooth, never ribbed, generally naked, but occasionally the yellowish epidermis is persistent; in the same individual, I have seen all the lower part of the shell thus covered and the upper part naked, the line of separation being defined. The _colour_ varies much, even sometimes considerably on the same individual; generally white or pale gray, with dull violet-coloured, longitudinal, moderately broad stripes; these stripes are sometimes equidistant, but more usually they are arranged so as to leave broad white spaces; the stripes fade away by endless variations, the edges of the compartments and the carinal end of the shell longest retaining any colour, until we have a uniformly white shell, generally covered with a yellowish epidermis; or the white is longitudinally marked with hyaline lines; this latter variety has a very peculiar aspect, and I did not doubt it was specifically distinct, until, in a number of specimens on a ship from the West Indies, I got the most perfect series, and another scarcely less perfect series from the Mediterranean, graduating into common coloured varieties.
Rarely the dull violet or purple stripes become approximate and dark, so that the whole shell is tinted of a brownish slate-colour, occasionally freckled with white. Again, we have another set of very pretty varieties, with a white or very pale pink ground, with either narrow bright pink or broad pinkish-purple stripes. Again, I have seen numerous specimens of a variety, _var. Stutsburi_, from the west coast of Africa, in which the upper part of the shell is white, and the lower part shaded with pinkish or dark purple approximate stripes, which often become confluent; in one group, the whole shell being thus uniformly coloured, without any vestige of stripes. I have seen another group from an unknown locality, in which the lower part of the shell was uniformly blueish-gray. A variety from Australia has narrow approximate dark claret-coloured stripes, transversely freckled with white. Lastly, in the variety _cirratus_, the whole shell is very pale purplish-brown, with indistinct longitudinal brownish stripes, transversely freckled with white lines. I considered this as a distinct species, until quite lately finding forms which I could not possibly determine whether to class as _B. cirratus_ or _amphitrite_. The radii are generally snow-white, or freckled with a bright mahogany tint, or rarely clouded with purple, or in the pink varieties with pink. The scuta are dull purple or pink, generally with a white band along their tergal margin; often, however, they are white, with merely one or two purple fasciæ. The thickness or strength of the shells varies much; some specimens attached to a floating cane, from Natal and the Philippine Archipelago, were extremely strong; others, from the Mediterranean and Australia, and some tubular varieties from the West Indies, were very thin, translucent, and fragile. _Size_: large specimens generally attain a diameter of from half to three quarters of an inch in basal diameter; and I have seen one or two specimens an inch in diameter.
_Scutum_; sometimes the surface is very smooth, but generally the growth-ridges are moderately prominent; the latter are occasionally very finely beaded, and this seems always the case with _var. cirratus_. Internally, the articular ridge is prominent and reflexed: the adductor ridge is sharp, very prominent, and straight; it runs parallel to the occludent margin; close to its lower side there is often a depression (Pl. 5, fig. 2 _i_), sometimes bounded by a slight ridge, as if for the attachment of a muscle, but there certainly is no muscle here: rarely the adductor ridge is only slightly prominent: there is a small and shallow little pit of variable depth for the lateral depressor muscle. _Tergum_ (2 _k_-2 _o_); this valve is here far more variable than in any other species: in the commonest purple-striped forms (2 _l_), the valve is rather broad, the basal margin lies in nearly a straight line on the opposite sides of the spur, which is placed at rather less than its own width from the basi-scutal angle; the spur is rather short, and in width about one fourth of the entire valve; its lower end is either bluntly pointed or more commonly nearly square (2 _k_) and parallel to the basal margin: in young specimens it is generally sharper than in older ones. Externally, in the line of the spur, there is either a slight longitudinal depression, or more rarely a deep furrow. The carinal margin is more or less convex, and is formed by upturned lines of growth: the scutal margin is broadly inflected. Internally, the articular ridge in the upper part is very prominent: the crests for the tergal depressor muscle are moderately prominent, but very variable. Sometimes the carinal portion of the basal margin is slightly hollowed out. In _var. Stutsburi_ (2 _m_, 2 _n_, 2 _o_), and in some white varieties, which differ most in the shape of the tergum from the commoner varieties, the whole valve is narrower, the spur is much sharper and narrower, the carinal half of the basal margin is much hollowed out and slopes down towards the spur, with the crests for the depressor muscles depending beneath the basal margin, and with the carinal margin sometimes extremely convex or protuberant. But the shape and position of the spur, and the outline of the carinal half of the basal margin vary much in nearly all the varieties.
_Compartments._--The upper parts of the parietal pores are either filled up solidly with, generally coloured, shell, or they are crossed by thin transverse calcerous septa: the longitudinal parietal septa occasionally bifurcate at their bases close to the outer lamina, making an irregular outer row of minute pores. The _Radii_ have their septa rather fine, and finely denticulated on both sides, but sometimes only on the lower side; the thickness of the septa varies a little; the interspaces are filled up solidly; the summits of the radii are jagged and oblique, and usually form an angle of about 45° with the basis, not being added to above the level of the opercular membrane; but not rarely they reach up much higher, and are very nearly parallel to the basis, extending from tip to tip of the compartments. Again, in some ordinary varieties, and always in _var. Stutsburi_, the summits of the radii are extremely oblique, the radii themselves forming a mere border to the compartments to which they belong. In no other species have I seen so great an amount of variation in the form of the summits of the radii. The _alæ_, in like manner, have their summits either very oblique, not being added to above the opercular membrane, or they are only slightly oblique; it often happens that in those specimens in which the summits of the radii are nearly parallel to the basis, the alæ are very oblique, and the converse: in other individuals, both radii and alæ have equally oblique summits. The sutural edges of the alæ vary in thickness, being either very thin and obscurely crenated, or moderately thick and ribbed. The _basis_ is porose; but I have never seen an underlying cancellated layer of shell, as is so common in several species.
_Mouth_: labrum, with from four to eight, generally with six, little teeth: mandibles with three teeth, and two minute lower teeth, or mere knobs: maxillæ with the edge straight, or with the inferior part forming a slightly step-formed projection. _Cirri_: the rami of the first pair are unequal by three or four segments, but in some specimens by five or six segments, with the front surfaces of the segments in the shorter ramus extremely protuberant. The second pair of cirri are short, with the front surfaces of the segments moderately protuberant: the third pair have a tuft of bristles at their bases on the thorax. The segments in the sixth pair have from four to six pairs of spines on the segments; equal-sized specimens seem to vary in this latter respect. There is a small sharp projection on the dorsal base of the penis. _Varieties._
With respect to _var._ 1, _communis_, I have nothing further to remark, except that I have seen specimens identically similar from the Mediterranean, Natal, the Philippine Archipelago, and Sydney; at the latter place it is said to be rare, but in most places it is the commonest variety, and is often attached to ships' bottoms. Of _var._ 2, _venustus_, I have seen specimens from the west coast of Africa, Natal, and Ceylon, in groups by themselves, and associated with _var. communis_; it is much less common than _var._ 1. The third variety, _pallidus_, is not uncommon; I have seen many specimens from the bottoms of ships, from the West Indies, and the west coast of Africa. Of the _var._ 4, _niveus_, I have seen the most perfect graduated series passing into _var._ 1, both from the West Indies, Florida, and the Mediterranean: I have seen other specimens from the Red Sea and Madagascar. Of the _var._ 5, _modestus_, I have seen only one group from an unknown locality; it is only remarkable from its uniform colouring.
The _var._ 6, _Stutsburi_, is more remarkable than the foregoing; until quite lately I did not doubt that it was specifically distinct; but as I have seen every character graduate into other varieties, I am now convinced that it is not a true species: all the specimens which I have seen have come on shells, or on ships' bottoms, from West Africa. Of _var._ 7, _obscurus_, I have seen three or four groups of specimens from unknown quarters, both on pebbles, shells, and on cork (probably from the Atlantic ocean); and likewise some specimens taken from the bottom of Her Majesty's ship "Fly," on the east coast of Australia; these latter are intermediate in character with the next _var. variegatus_; from the Australian seas, which I at first ranked as an undoubted species, but I have subsequently failed in discovering any sufficient diagnostic character. Lastly, of _var. cirratus_, I have seen several groups of specimens from India and the Philippine Archipelago, and a group intermediate in character between this and the first and third varieties, from Australia; I retained this variety owing to its peculiar freckled, pale brown colouring and beaded scuta (of which, however, I have seen decided traces in the common variety), as a distinct species, after I had given up all the foregoing forms. I entertain some doubts whether I have now acted right; but when I found some specimens which, I found it impossible to decide, whether to rank as _amphitrite_ or _cirratus_, I determined to take the more prudent course, and sink the latter as a species. This variety, also, seems to connect _B. amphitrite_ and _concavus_ very closely.
20. BALANUS PŒCILUS. Pl. 5, fig. 3 _a_, 3 _b_. _Shell dull red, freckled with white. Scutum internally without an adductor ridge; tergum with the spur, sharply truncated, almost one third of width of valve._ _Hab._--West coast of South America, Mus. Cuming; attached to an Avicula. The appearance of the fragile shell, in the one group of specimens which I have seen, leads me to suspect that they may have grown under unfavorable circumstances. This species differs considerably in general aspect, but not much in essential characters, from _B. amphitrite_; the absence, however, of an adductor ridge to the scutum, and the sharply truncated spur of the tergum, are sufficient to distinguish them. In the opercular valves this species comes near to _B. vinaceus_, also from the west coast of South America; but the striated scuta of that species, the cancellated inner lamina of the parietes, the general colouring, and square porose radii, are amply diagnostic characters. _General Appearance._--Shell fragile, tubulo-conical, orifice large, passing from diamond-shaped into oval. Colour fine dark rose, freckled with transverse, sharply pointed, fine zig-zag white lines: the pink is also so arranged as to obscurely give to the walls a longitudinally striped appearance: radii generally rather whiter than the walls, and similarly freckled: terga similarly freckled: scuta dull red, with a white band along the scutal margin. Basal diameter of largest specimen half an inch.
_Scutum_, externally smooth: internally, articular ridge moderately developed, slightly reflexed: there is no adductor ridge: there is a distinct pit for the lateral depressor muscle. _Tergum_, with the scutal margin unusually prominent, toothed: longitudinal furrow shallow, the edges apparently having no tendency to fold in: spur short, barely one third of width of valve, with the lower end sharply truncated, parallel to the basal margin: articular ridge and crests for the depressores moderately prominent. _Compartments._--Walls very fragile, with the outer lamina not thicker than the inner lamina. _Radii_ fragile, broad, with their summits moderately oblique; their sutural edges have the septa plainly denticulated on both sides, with the interspaces filled up solidly nearly to the tips of the septa. _Alæ_, with their summits more oblique than those of the radii; their sutural edges smooth. _Basis_ with an underlying cancellated layer. _Mouth_: labrum with three unusually large teeth on each side of the notch: mandibles with the fourth tooth tolerably well developed, the fifth being confluent with the inferior angle. _Maxillæ_ simple. _Cirri_,--first pair with one ramus longer by about four segments than the other ramus, which has considerably protuberant segments: second pair with segments only moderately protuberant: sixth pair with segments much elongated, but bearing only four pairs of spines. 21. BALANUS EBURNEUS. Pl. 5, fig. 4 _a_-4 _d_. BALANUS EBURNEUS. _Aug. Gould_ (!). Report on the Invertebrata of Massachussetts, 1841, fig. 6.
_Shell yellowish white. Scutum striated longitudinally: tergum with the spur truncated, the basi-carinal margin generally much hollowed out, and the carinal margin protuberant in the upper part._ _Hab._--United States, from about lat. 42° to Charlestown; West Indies; Honduras; Venezuela; attached to shells and floating wood. Attached to ships' bottoms from Trinidad and Jamaica, associated with _B. tintinnabulum_, _amphitrite_, and _improvisus_. Brackish water, Salem, Massachussetts, according to Mr. Stimpson. Mus. Aug. Gould, Agassiz, Stutchbury, Cuming, W. Dunker, &c.; very common. _General Appearance._--Shell conical, or almost tubular; white, with the surface very smooth, covered by thin yellowish epidermis, but with the radii naked. Orifice large, passing from rhomboidal into pentagonal, moderately toothed. Average full size, about one inch in basal diameter; I have seen a specimen 1.3 in basal diameter, and the same in height.
_Scutum_, plainly striated longitudinally: the teeth on the occludent margin small. Internally, the upper surface is roughened: the articular ridge is prominent, and either slightly or not at all reflexed: the pit for the adductor muscle is distinct; the adductor ridge is prominent in a variable degree, and is almost confluent with the articular ridge. In one specimen from Beverly Bay, U. S., the scuta were extraordinarily disintegrated, and I could perceive no trace of the external radiating striæ. _Tergum_, with the basal margin on the carinal side of the spur sometimes deeply (Pl. 5, fig. 4 _b_), and sometimes only slightly (fig. 4 _d_), and rarely hardly at all, hollowed out: when much hollowed out the valve may almost be said to be two-pronged, with the carinal prong narrower than the spur. There is no distinct longitudinal furrow, but the whole scutal margin projects above the general surface of the valve. In the carinal margin, in the upper part, there is a remarkable convexity or protuberance in the same plane with the valve, from which it is separated by a very slight and narrow ridge. The spur is about one fourth of the width of the valve, with its lower end abruptly truncated. Internally, the upper surface is much roughened with finely crenated ridges: the distinct crests for the depressores cover the whole of the so-called carinal prong.
Text from Project Gutenberg, public domain in the United States.