A Monograph on the Sub-class Cirripedia · Charles Darwin
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To _var. coccopoma_ (Pl. 1, fig. _d_) I alluded in my introductory remarks as having so strongly the aspect of a distinct species. I possess a beautiful group, with a globulo-conical, smooth shell, of the finest rose colour, with a rather small, rounded orifice. These specimens were attached (mingled with _B. trigonus_) to _Avicula margaritifera_, from, as Mr. Cuming believes, Panama. I can never look at this set of specimens without doubting the correctness of the determination at which I have arrived. In the British Museum there are two sets of specimens taken off a vessel, on the west coast of South America, almost identical in external appearance with those in my possession, but rather more rugged. Mr. Stutchbury has sent me some specimens from a ship, direct from China, which are rather paler pink, and more striped, and come near to some ordinary varieties of _B. tintinnabulum_. The scuta (Pl. 2, fig. 1 _f_) in the above three sets of specimens agree in having the adductor ridge more developed, and the pit for the lateral depressor muscle deeper than is usual. The tergum (1 _l_, 1 _o_) in most, but not in all these specimens, has a rather broader spur; and some of the specimens have the carinal portion of the basal margin considerably hollowed out; the spur, also, is placed nearer the basi-scutal angle than in ordinary cases. On the other hand, in Mr. Cuming's collection, there are two specimens taken off a vessel, identical in external appearance with the foregoing, but which have scuta and terga in every character exactly as in _var. communis_; hence I am compelled to consider all these specimens as mere varieties.
_Var. concinnus_ (Pl. 1, fig. _e_) is, perhaps, the most remarkable of all the varieties; I have seen three sets of specimens from the west coast of South America,--all identical in appearance, having longitudinally-ribbed walls, either rosy or of a dull purple, striped and freckled in a peculiar manner with white. I have, however, seen an approach to this colouring in some few specimens of _var. communis_; and the shell itself offers no other peculiarities. The scutum (Pl. 2, fig. 1 _g_) resembles, in general shape, that of _var. coccopoma_; but the adductor ridge is here much sharper and more prominent; and the rostral depressor muscle, instead of being lodged in a little cavity formed by the folding over the occludent margin, has, in addition, a small plate on the under side, which tends to convert the pit into a tube. The tergum exactly resembles that of _var. communis_. The segments in the sixth cirrus bear six, instead of four, pairs of spines,--a circumstance which I have noticed only in some young specimens of _var. communis_, from the Cape of Good Hope. From these several peculiarities, until quite lately, I resolved to keep this form specifically distinct; but I have finally concluded that they are not sufficient. For firstly, I have seen a scutum in _var. communis_ (Pl. 2, fig. 1 _d_), with the adductor ridge nearly as sharp; and this ridge is always strongly pronounced in _var. coccopoma_; secondly, with respect to the plate for the rostral depressor muscle, although I have not seen this in any other variety, yet in _Bal. concavus_ a closely analogous plate, situated in the lateral depressor cavity, is highly variable, and I am not willing to found a new species on one minute point of structure,--a structure which is variable in another species of the same genus.
I have seen some cylindrical and conical specimens of _B. tintinnabulum_, from the coast of Mexico and California, only noticeable, as far as the shell was concerned, from being rugged, and of a dull blueish-purple; but which had opercular valves exactly like those of _var. coccopoma_, and therefore, as far as the scutum is concerned, approaching closely in structure to _var. concinnus_,--all three from the west coast of America. Hence I was at one time led to believe that there existed a species on this line of coast, which represented _B. tintinnabulum_, and which varied in external shape and colour in an analogous manner to that species. But as the opercular valves in _var. coccopoma_ are sometimes identical with those of _var. communis_, and as this is always the case with the tergum of _var. concinnus_, and as the shell itself presents no differences, it is scarcely possible to admit the existence on the west coast of America of this supposed representative of _B. tintinnabulum_. With respect to _var. intermedius_ I have little to say in addition to the character given above: I have seen only two groups of specimens in Mr. Cuming's collection: the chief interest in this variety is that it shows that the next form must be ranked as a variety, and not as a distinct species.
Of _var. occator_ (Pl. 1, fig. _k_) I have seen several specimens, mostly taken off the bottoms of vessels, and one specimen, marked in Mr. Cuming's collection "South Seas." After having carefully examined these specimens, I came to the conclusion, that the slightly oblique radii--the general colouring, and more especially that of the sheath--the scuta (Pl. 2, fig. 1 _b_), with their sharp hood-like points, in radiating lines--and the terga, with the spur so near to the basi-scutal angle, were amply sufficient to distinguish it as a good species. Subsequently, however, I found that the scuta in _var. crispatus_ presented, both externally and internally, exactly the same peculiar appearance. In _var. intermedius_, I found the summits of the radii equally oblique, and the general colouring nearly the same, and more especially a close approach to the singular circumstance of the sheath differing in colour towards the opposite ends of the shell. So that the position of the spur of the tergum was the chief remaining character; and this evidently varied considerably in the four or five specimens examined by me, being either its own width, or much less than its own width, from the basi-scutal angle: the outline, also, of the small portion of basal margin, between the spur and the basi-scutal angle, likewise varied much, being either angularly indented, or gradually curved down towards the spur: so also the tip of the spur varied in shape. The longitudinal furrow is unusually apt, in this variety, to remain open. We know that the position of the spur varies considerably in _var. communis_. Hence, although the spur, on an average, lies closer to the basi-scutal angle in this than in any other variety, even than in _var. d'Orbignii_, it would, I conceive, be preposterous to found a species on this one character. In the animal's body, every part agrees perfectly with that of _var. communis_.
Lastly, we come to _var. d'Orbignii_ (Pl. 1, fig. _l_): until quite recently I did not even suspect that this form was only a variety of _B. tintinnabulum_: I have examined a great number of specimens in Mr. Stutchbury's collection, which had come attached on a vessel from Java, and likewise a few other specimens in other collections. They all closely resemble each other in shape, and even in size, and differ only in tint of colour, and in the surface being either very smooth, or longitudinally ribbed, sometimes with rugged, sharp points. From this circumstance--from the peculiarity of the tint, with the tips of the parietes and one side of the radii perfectly white--and from the obliquity of the summits of the radii, I was led to think this form specifically distinct. But the colour does not differ from that of some other varieties of _B. tintinnabulum_; the circumstance of the colour being uniform or not striped, is common to the sub-varieties of several varieties, and the white tips to the parietes, and the white borders to the radii, result simply from the shell, whilst young, having been wholly white, and this is not rarely the case with _var. communis_.
Dismissing, therefore, colour, it will be found that hardly any other characters remain by which this form can be separated from _var. occator_; in both the summits of the radii are oblique, in both the sheath is coloured in nearly the same manner, in both the opercular valves, especially the terga (Pl. 2, figs. 1 _m_, 1 _n_), resemble each other; the scuta, however, are smooth in _var. d'Orbignii_ and rough in _var. occator_. This latter form, certainly, cannot be specifically separated from _var. intermedius_, and this assuredly is only a variety of _B. tintinnabulum_. Hence I am led to conclude that _Balanus d'Orbignii_ of Chenu, peculiar as its whole aspect is, must be ranked only as a variety of _B. tintinnabulum_; its oblique radii resulting from the same cause, whatever that may be, which has given this structure to _var. intermedius_ and _occator_; and its peculiar colouring to having been exposed (owing probably to having been transported on vessels) to different conditions, whilst young and old. 2. BALANUS TULIPIFORMIS. Pl. 2, fig. 2 _a_-2 _d_. BALANUS TULIPIFORMIS EX CORALLIO RUBRO. _Ellis._[88] Philosoph. Transactions, vol. 50 (1758), tab. 30, fig. 10. LEPAS TULIPA. _Poli._ Test. utriusque Siciliæ, tab. 5, fig. 1. et 6 (1791). BALANUS TINTINNABULUM (_var._) _Chenu._ Illust. Conch., tab. 3, f. 5.
_Hab._--Sicily, Malta, Malaga, (associated with _B. perforatus_), Madeira. Often growing in clusters and associated with _Pachylasma giganteum_. Attached to _Millepora aspera_, oysters, and other shells. According to Poli, an inhabitant of deep water; yet in mus. Cuming there are two fine specimens attached to the always floating _Lepas anatifera._ Mus. Lowe, Macandrew, Stutchbury. _General Appearance._--Shell tubulo-conical or conical: orifice large, toothed, approaching to pentagonal. Surface moderately smooth, naked. Colour rosy, or tile-red, with a slight tinge of purple; or beautiful rich purple. Radii nearly as dark as, or darker than, the parietes. The portion of the alæ seen externally is generally white. Internally the whole shell is nearly white. Generally the tints outside vary in transverse fasciæ; sometimes there are very fine, dark, longitudinal lines. Largest specimen (from Malta), 1.4 of an inch in basal diameter; usually full-sized specimens are about three quarters of an inch in basal diameter. _Scuta_ (Pl. 2, fig. 2 _a_, 2 _c_) very smooth, with the growth-ridges very little prominent, sometimes there are obscure traces of longitudinal striæ; surface covered by an unusually thick and persistent yellow membrane: valve narrow, with the upper part commonly reflexed: the basal margin forms, with the occludent margin, a smaller angle than is usual: the tergal margin of the valve is rectangularly inflected, instead of being, as is usual, merely bowed inwards. Internally, the articular ridge is rather prominent. The depth of the _slight_ pit for the lateral depressor muscle is variable; it sometimes includes a minute, central, longitudinal ridge.
_Terga_ (2 _b_, 2 _d_): the longitudinal furrow is deep, with the sides folded in; the spur is placed at about its own width from the basi-scutal angle; it is moderately long, with its lower end obliquely rounded off; but the length, breadth, and precise outline of the lower end varies a little. The basal margin on the opposite sides of the spur, forms a nearly straight line, but with the portion on the carinal side very slightly hollowed out. Crests for the depressor muscle are well developed. _Compartments._--The radii and alæ always have their summits oblique: the sutural edges of the radii are deeply penetrated by pores between the strongly denticulated septa: the sutural edges of the alæ are quite smooth: the tubes in the parietes are crossed in the upper part of the shell by septa. _Basis_ tubular, with an underlying cancellated mass. _Mouth._--Labrum with the teeth either absent or very small: mandibles with the fourth and fifth teeth rudimentary: maxillæ with a small notch under the two upper spines; near the lower angle, two spines, one beneath the other, are larger even than the upper pair; beneath the lower pair, there is a tuft of fine spines. _Cirri_, segments protuberant in one ramus of the first cirrus and in both rami of the second cirrus; posterior cirri with the segments short and broad, each bearing three pairs of spines, with a small intermediate tuft.
_Affinities._--This species in all essential respects comes very near to the three last varieties of _B. tintinnabulum_, which have the orifices of their shells toothed. The smoothness of the scutum, with its persistent epidermis,--its peculiar shape,--its small and not reflexed articular ridge,--together with the crests on the tergum for the depressor muscles, are sufficient diagnostic characters. Even in general habit and tint of colour, this species has a different aspect from _B. tintinnabulum_. In some respects _B. tulipiformis_ leads into the species included in the third section of the genus. 3. BALANUS PSITTACUS. Pl. 2, fig. 3 _a_-3 _d_. LEPAS PSITTACUS. _Molina._ Hist. Nat. Chile (1788), vol. i, p. 223. BALANUS PICOS. _Lesson._ Zoolog. Voyage de la Coquille (1829). ---- TINTINNABULUM (var. c). _Ranzani._ Mem. di Storia Nat. tab. 3, fig. 1-3 (1820). ---- CYLINDRACEUS. _Lamarck_, in _Chenu_. Illust. Conch. Tab. 4, fig. 17, Tab. 5, fig. 7, sed non var. (_c._) in Lamarck, Animaux sans Vert., (1818). ---- PSITTACUS. _King_ and _Broderip_. Zoolog. Journal, vol. v (1832-1834), p. 332. _Shell, pale dirty pink; orifice hexagonal. Scutum with the articular ridge very small, confluent with the very prominent adductor ridge, forming a tubular cavity, which extends up to the apex of the valve. Tergum with the apex produced, needle-like, purple: spur placed at less than its own width from the basi-scutal angle._
_Hab._--Peru, Chile, Chiloe, Patagonia. Fossil in an ancient tertiary deposit, Coquimbo; and in a superficial, recent bed at S. Josef, in Patagonia. _General appearance._--Shell either almost cylindrical or steeply conical, generally flesh-coloured, sometimes pale pink; surface either smooth (when not disintegrated) or sometimes with the parietes distinctly and rather strongly ribbed, with the ribs distant from each other: I have seen six or seven ribs on the rostrum alone. The orifice in the most perfect specimens is nearly equilateral and hexagonal. The radii generally are very broad, but occasionally quite narrow, and even linear. The basis is generally deeply and irregularly cup-formed. _Size._--This is the largest species in the family: I have seen a specimen six inches in length and three and a half in diameter; and another specimen no less than nine in length, though only two and a half inches in diameter.
_Scuta._--In full-sized specimens the surface is finely striated longitudinally, caused by the lines of growth being minutely sinuous; but in young specimens, until they attain a basal diameter of above half an inch, the surface is smooth. The valve is transversely arched, a line of flexure running from the apex to the basal margin, at about one third of the width of the valve from the tergal margin. The basal margin is curved nearly continuously, and extends nearly half-way up the valve; hence the basi-tergal corner is largely rounded off. The articular ridge is but little prominent, and is not reflexed: the articular furrow is very narrow. The adductor ridge consists of a sharp, much-projecting plate, running down close to the basal margin, and is confluent with the lower part of the articular ridge. This plate and the inflected tergal margin of the valve, together form a large and deep cavity, which extends up almost to the apex of the valve. The depressor muscle is attached in the middle, at the lower, open end of this cavity.
_Terga._--These are strongly beaked, the beak being from one third to one fourth of the total length of the valve, including the spur: the beak is very sharp, somewhat flattened, and bowed; when young, and when well preserved, it is coloured purple: it is penetrated by a fine tubular cavity, occupied by a thread of corium, which extends about half-way up it. The whole valve is narrow, being about thrice as long as wide. The spur is also long and narrow; it is seated at less than its own width from the basi-scutal angle. The scutal margin is not much inflected. The longitudinal furrow has its sides, in full-grown specimens, closely folded together. The basal margin slopes down on both sides to the spur. There are no crests, or only traces of them, for the attachment of the depressor muscle. Internally, the spur is prolonged, as a prominent ridge, upwards to the beak, and serves as an articular ridge. In the middle, in the upper part (Pl. 2, fig. 3 _d_), between this articular ridge and the carinal margin, there is a second narrow ridge, which extends from the lower part of the beak half-way down the valve, and then dies out. The space between these two ridges, and the ridges themselves, are coloured purple, and consist of harder shell than the rest of the valve; hence, when the outer surface and the adjoining scutal and carinal margins disintegrate, this part remains, and so forms the beaked, purple apex.
_Compartments._--The parietal tubes are unusually large in proportion to the size of the shell, and run up to the summit without any transverse septa: the longitudinal septa are strongly denticulated. The radii are penetrated by large tubes; their septa are very strongly denticulated, and the denticuli themselves often subdivide and branch out at their extremities. The sutural edges of the alæ are smooth, or with a high power can just be seen to be crenated. The radii are generally very highly developed, so that their summits are even wider than the bases of the parietes; but, on the other hand, in some few large specimens, the radii are either very narrow or absolutely linear. In these latter cases, the diametric growth has nearly or altogether ceased, whilst the walls of the shell have continued to be added to at their bases, their summits at the same time suffering disintegration; and thus the orifice has increased in size. _Basis_ generally, and occasionally very deeply, cup-formed. An unusually thick cancellated layer in most cases forms the under side of the basis. _Mouth._--Labrum apparently without teeth, or with very minute ones: mandibles with three teeth, of which the third is thicker than the first or upper one: the fourth and fifth teeth are confluent with the inferior angle. The maxillæ have a small notch under the upper pair of spines; inferior part projecting and supporting two spines, placed one below the other, and equalling in size the upper pair. _Cirri_: the rami of the first cirrus are unequal by four or five segments; shorter ramus and both rami of the second cirrus with the segments extremely protuberant: posterior cirri not much elongated, with the segments rather broad, supporting six pairs of spines.
_General Remarks._--This, which is much the largest known species of the genus, ranges from Peru (Arica being the most northern spot, whence I have seen specimens), along the coast of Chile, where it is very abundant at a few fathoms' depth, at least as far south as Southern Chiloe; it is said by Captain King to attain the largest size at Conception. On the coast of Eastern Patagonia, I dredged up this species from nineteen fathoms, in lat. 49°. In lat. 42° (S. Josef), on the same eastern coast, I found fossil specimens in beds of sand upraised between eighty and one hundred feet. In the tertiary formation at Coquimbo, in Chile, it occurs in the middle bed, associated with the recent _B. lævis_, and with various mollusca, all of which are apparently extinct, indicating that the formation is of considerable antiquity. In the living state, on the coast of Chile, it is often associated with _B. lævis_. As it frequently adheres to large specimens of the Concholepas, it must sometimes be an inhabitant of shallow water. I have seen one specimen attached to _Mytilus Magellanicus_. Mr. Cuming believes that about six fathoms is the usual depth at which it lives. Numerous specimens are often congregated together into great masses.
Mr. Stutchbury has some interesting specimens which he procured from a ship that had first sailed to Ichaboe, on the coast of Africa, and afterwards to Patagonia; consequently numerous specimens of _B. psittacus_ had become attached on _B. tintinnabulum_, and subsequently during the voyage home, some few of the latter again had adhered on _B. psittacus_: the contrast in the paler colour and hexagonal orifice of this species, with the darker tints and more trigonal orifice of _B. tintinnabulum_ was striking. At Coquimbo, in Chile, I procured a specimen of _B. psittacus_, attached to a chain cable which had been in the water only six months; this specimen measured 1.3 of an inch in basal diameter, and .8 in height: this shows a rapid rate of growth. Lastly, I may mention that it is asserted by Molina, and I am assured by Mr. Cuming that the statement is perfectly correct, that this Balanus, when cooked, is universally esteemed as a delicious article of food. 4. BALANUS CAPENSIS. Pl. 2, fig. 4 _a_, 4 _b_. BALANUS CAPENSIS ORE OBLIQUO. _Ellis._ Phil. Transact., vol. 50 (1758), Tab. 34, fig. 14. _Shell shaded, and often longitudinally striped with bright pink. Scutum as in B. psittacus. Tergum with the apex produced and needle-like, white: spur placed at its own width from the basi-scutal angle._
_Hab._--Cape of Good Hope. Attached to stems of Fuci, Algoa Bay. Mus. Brit. and Bowerbank. Attached to a Patella, Mus. Darwin, Mus. Cuming, and Stutchbury. Attached to floating kelp, Lagulhas Bank, Mus. James Ross, associated with _B. tintinnabulum_ and _spongicola_. This species comes extremely close to the South American _B. psittacus_, and I should hardly have attached a specific name to it, had I not examined many specimens, young and old, of the true _B. psittacus_, from Peru, Chile, and Eastern Patagonia, and found them all identical in the few, apparently trifling points, in which that species differs from _B. capensis_. The animal's body and the shell agree in every respect, excepting that the shell is decidedly pinker, being often most distinctly and prettily striped longitudinally with pale and bright pink. In some of the specimens the basis is cup-formed: in some, the broad radii are pale pink, in others they are quite white, and in this latter case a singular aspect is given to the pinkish varieties. In very large specimens (and I have seen one fully two inches in basal diameter) the pink colour is extremely feeble, and the whole shell has a very rugged, disintegrated, coarse, and sometimes dirty appearance: in most of these large specimens the walls are more massive than in _B. psittacus_, and the orifice of the shell rather smaller; in some, however, the walls certainly are of unusual thinness.
The _Scuta_ differ from those of _B. psittacus_ only in the basi-tergal corner not being so much rounded off, and consequently in the articular ridge, which is rather more reflexed, descending in proportion lower down the valve: the cavity at the basi-tergal corner is in proportion broader. The valves in the two species differ, also, but only in young specimens, in the occludent half being tinted, both externally and internally, purple, whereas in _B. psittacus_ the whole valve, at all ages, is white. In the _terga_ the spur is removed fully its own width from the basi-scutal angle, whereas it is not half this distance in _B. psittacus_. The scutal margin is here much more inflected. In _B. psittacus_ there is a remarkable patch of purple on the inside of the valve, between the articular ridge and a second special ridge; of this purple patch there is here no trace, consequently the beak or apex is white. The beak, also, is less prominent. The special ridge, just alluded to, here runs much nearer to the articular ridge, and is less prominent: indeed, in old specimens, it is often almost obliterated. Finally, the whole valve, in proportion to the Scutum, is rather broader.
I have seen a young specimen, about a quarter of an inch in basal diameter, with the orifice of the shell toothed owing to the obliquity of the summits of the radii; and this gave the shell a very peculiar aspect. The largest well-coloured specimen which I have seen is 1.2 of an inch in basal diameter; but in Mr. Cuming's collection there are two rugged, disintegrated specimens, two inches in basal diameter, and two and a half in height. Some specimens, 1.3 in basal diameter, in Mr. Stutchbury's collection, are remarkable from the radii having been obliterated--the shell being merely divided by six sutures, as we have seen is likewise sometimes the case with large specimens of _B. psittacus_. This species is evidently a South African representative of the South American _B. psittacus_. 5. BALANUS NIGRESCENS. Pl. 2, fig. 5 _a_, 5 _b_. BALANUS NIGRESCENS. _Lamarck_, (1818) in _Chenu_. Illust. Conch., Tab. 4, fig. 16. ---- GIGAS. _Ranzani._ Memoire di Storia Nat., 1820, Tab. 3, fig. 5, 6, 7. ---- ---- _De Blainville._ Dict. des Sc. Nat., Tab. 116, fig. 2, 2 _a_. _Shell cinereous, tinted with pale or blackish blue, or wholly white. Scutum with the articular ridge terminating downwards in a small, sharp, free point: adductor ridge prominent. Tergum with the apex produced and needle-like._ _Hab._--Swan River, West Australia, Mus. Brit., attached to sandstone. Attached to sandstone and to each other in a group, Mus. Cuming. Twofold Bay, S. E. Australia, attached to tidal rocks and Patellæ, Mus. Darwin.
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