Section A.

1. BALANUS TINTINNABULUM. Pl. 1, fig. a-l; Pl. 2, fig. 1 a-1 o.

LEPAS TINTINNABULUM. Linn. Syst. Naturæ, 1767.

---- ------------ Ellis. Phil. Transact., vol. 50, 1758, Tab. 34, figs. 8 and 9.

---- ------------ Chemnitz. Neues. Syst. Conch., 8 B. (1785), Tab. 97, figs. 828-831.

BALANUS TULIPA. Bruguière. Encyclop. Meth., 1789; sed non B. tulipa alba, in Chemnitz; neenon B. tulipa, O. F. Müller, Zoolog. Dan.; neenon B. tulipa, Poli, Test. ut. Siciliæ.

------ ---- G. B. Sowerby. Genera of Recent and Fossil Shells, Tab. Genus Balanus.

LEPAS CRISPATA (var.) Schröter. Einleitung Conch. vol. iii, Tab. 9, fig. 21.

---- SPINOSA (var.) Gmelin. Linn. Syst. Nat.

---- TINTINNABULUM, SPINOSA, CRISPATA ET PORCATA. W. Wood. General Conchology, 1815, Pl. 6, figs. 1, 2. Pl. 7, figs. 4, 5. Pl. 8, figs. 1-5.

BALANUS TINTINNABULUM. Chenu. Illust. Conch.[87]

------ D’ORBIGNII (var.) Chenu. Illust. Conch., Tab. 6, fig. 10, sed non Tab. 4, fig. 13.

------ CRASSUS (Foss.) Sowerby (!). Min. Conch., 1818. Tab. 84.

Shell varying from pink to blackish purple, often striped and ribbed longitudinally: orifice generally entire, sometimes toothed. Scutum with the articular ridge broad and reflexed. Tergum with the basal margin generally forming a straight line on opposite sides of the spur.

Var. (1) communis (Pl. 1, figs. a, b, f supra; Pl. 2, figs. 1 a, 1 c, 1 d, 1 e, 1 i, 1 k): conical or tubulo-conical; smooth or moderately ribbed longitudinally; colours varying from purplish-pink to blackish-purple; often in obscure longitudinal stripes; orifice of shell rounded-trigonal.

Var. (2) vesiculosus (young) (Pl. 2, fig. 1 h): exterior surface of the scuta impressed with small square holes, arranged in two or more rows, radiating from the apex of the valve.

Var. (3) validus (Pl. 1, figs. c, f infra): globulo-convex; coarsely ribbed, ribs flexuous; either smooth or rugged; pale chocolate purple or pink; shell extremely strong; orifice almost circular.

Var. (4) zebra (Pl. 1, fig. g): conical; rich chocolate purple with broad snow-white ribs; sheath bright chesnut colour; summits of alæ oblique; orifice almost circular.

Var. (5) crispatus (Schröter) (Pl. 1, fig. h): pale blueish or pinkish-purple, with irregular rough projections, or with short, sharp, needle-like points; scuta with their exterior surface either plain, or with radiating lines formed of hood-like projecting points.

Var. (6) spinosus (Gmelin) (Pl. 1, fig. i): globulo-conical or cylindrical; shell rather thin, with long, upcurved, nearly cylindrical, very sharp points; colours very pale; attached to other specimens, and to Lepas anatifera.

Var. (7) coccopoma (Pl. 1, fig. d; Pl. 2, fig. 1 f, 1 l, 1 o): globulo-conical; orifice small, rounded; walls generally smooth, thick; intense rose-colour, sometimes most faintly striped longitudinally with varying shades of pink; radii tinged with purple; scutum sometimes as in var. communis, sometimes with its basi-tergal corner much cut off, with the adductor ridge prominent, the pit for the depressor muscle deep, and the articular ridge broad and hooked; tergum sometimes as in var. communis, sometimes with a broader spur, placed nearer to the basi-scutal corner of the valve.

Var. (8) concinnus (Pl. 1, fig. e; Pl. 2, fig. 1 g): globulo-conical; walls finely ribbed; dull purple, tinged and freckled with white; scutum, with a broad, hooked, articular ridge, with an extremely sharp plate-like adductor ridge, and with a cavity, bordered by a plate, for the rostral depressor muscle; tergum as in var. 1.

Var. (9) intermedius: radii with their summits slightly oblique; parietes pale blueish purple, with narrow dark purplish-blue longitudinal lines; sheath with the internal surface of the rostrum and lateral compartments much darker colored than the internal surface of the carina and carino-lateral compartments; scuta and terga as in var. communis.

Var. (10) occator (Pl. 1, fig. k; Pl. 2, 1 b): radii with their summits slightly oblique; parietes smooth, or ribbed, or spinose; very pale blueish-purple, with narrow darker longitudinal lines; sheath with the internal surface of the rostrum and lateral compartments dull blue, whilst the corresponding parts of the carina and carino-lateral compartments are white; scuta with small, sharp, hood-formed points, arranged in straight radiating lines; terga with the spur placed at either its own width, or less than its own width, from the basi-scutal angle.

Var. (11) d’Orbignii (Chenu) (Pl. 1, fig. l; Pl. 2, 1 m, 1 n): radii with their summits oblique, and the orifice of the shell rather deeply toothed; shell conical or tubulo-conical, smooth, or rugged; colour dull purplish-lilac, with the tips of the parietes and a band along one side of the radii quite white; sheath rather darker at the rostral than at the carinal end; scuta as in var. 1; terga as in var. occator.

Habitat.—West coast of Africa, on mytili; Madeira, on rocks; West Indies; Cape of Good Hope, on a patella and on kelp; mouth of the Indus; East Indian Archipelago; Sydney, Australia, attached to Lepas anserifera, adhering to a floating cane; Peru; Galapagos Islands; West Mexico; California. Extremely common on ships’ bottoms arriving from West Africa, India, and China, often associated with B. amphitrite.

Fossil Red Crag, England; Mus. S. Wood and J. de C. Sowerby.—Touraine (?); Mus. Lyell.

General Remarks.—This, the first species of Balanus, is, perhaps with the exception of B. amphitrite, the most difficult and variable in the genus. There are some other species which vary quite as much in external appearance; for instance, B. perforatus; but B. tintinnabulum also varies in far more important points, as in the proportions and structure of the opercular valves. The difficulty in determining whether or not the differences are specific, is wonderfully increased by whole groups of individuals varying in exactly the same manner. I have seen three most distinct varieties taken from the bottom of the same vessel, so that I did not at first entertain the least doubt that they were three distinct species. I may mention, as showing the vacillations which I have experienced on this subject, that beginning with the impression, that the above three varieties were really distinct species, after going over the several immense collections of specimens placed at my disposal, I came to the conclusion that the above three, and several other forms presently to be described, were only varieties; yet after an interval of some months, having to look at some of these specimens again, I could not but think that I had come to a false conclusion, and so went into all the details again, and satisfied myself that I had followed a right course; after another interval, I had to repeat the same process, and even now I can never look at a group of the beautifully coloured shells with their small rounded orifices of var. coccopoma attached to the Avicula margaritifera, or again at var. d’Orbignii, with its toothed orifice and white tips to the compartments, without thinking that they must be specifically distinct from the dull-coloured specimens with large entire orifices so common on ships’ bottoms; yet I can produce a full series of intermediate forms, and I can further show, in each variety, that the several points of difference by which each is characterised, are variable. I may be permitted to add, in order to show that it has not been from indolence that I have combined so many forms, that I had named and already written out full descriptions of most of the varieties, before determining to sacrifice them.

Seeing that B. tintinnabulum and amphitrite are the two most variable species in the genus, more especially in the important characters derived from the opercular valves, and knowing that these species are attached so very frequently to ships’ bottoms, one is led to suspect that their extreme tendency to vary may be due to their being exposed to varying and peculiar conditions, whilst transported to new and distant localities. It is even just possible, as may be inferred from the facts given in the Introduction (p. 102) in regard to certain monstrous specimens of Bal. balanoides having been apparently impregnated by adjoining individuals, that the varieties may interbreed, and so produce numerous intermediate forms. Whether or not this could take place, I am inclined to look at these two species, as in an almost analogous condition with our domestic animals, which give rise to such infinitely numerous varieties. It appears to me probable, that several of the varieties keep true to their peculiarities, as long as they continue to breed in the same locality; but that when their larvæ become attached to ships’ bottoms, and are thus transported and exposed to new conditions, they give rise to new and ever-varying varieties. I will first give a full description of the more common forms of B. tintinnabulum, which undoubtedly belong to the same species, only alluding to the less frequent points of difference, and then separately describe the more marked varieties.

General Appearance.—Shape of shell generally tubulo-conical, or conical, or globulo-conical, rarely depressed. Orifice either large and rounded-trigonal, or small and oval, either entire or less frequently toothed. Surface quite smooth, or longitudinally ribbed; ribs of variable strength, not unfrequently flexuous or branching, sometimes roughened with blunt or sharp projecting, irregular points, or more rarely with almost cylindrical, upturned, long spines; the simple longitudinal ribs are generally most strongly marked in young specimens. Colour, generally varying from pink, to pink tinged with purple, to dark, inky purple, more or less striped, longitudinally, with white or pale tints; rarely the shell is of the brightest rose-colour, either uniform or longitudinally striped; sometimes it is pale purplish, or dark blue; and sometimes dark chocolate-purple: the ribs, when present, are generally more or less white, sometimes snow-white. That there is much variation in colour, and in the prominence of the longitudinal ribs, is quite certain, as the two sides of the same individual sometimes differ greatly in these respects. The radii are generally rather darker coloured than the parietes, but sometimes they are lighter, even in the darkest tinged specimens. The surfaces of the radii are occasionally finely plaited in lines parallel to the basis. In some infrequent varieties the radii have oblique summits, making the orifice of the shell to be toothed. The sheath is generally feebly coloured, but sometimes bright chesnut-brown, and sometimes blueish. The strength of the shell varies considerably; some of the globulo-conical varieties are extremely massive. Size; basal diameter of largest specimen very nearly three inches; height of the highest specimen three inches.

Young specimens are apt to have a peculiar aspect; for their shell is often strongly ribbed longitudinally, and the summits of their radii are sometimes oblique. Their scuta are sometimes deeply pitted in radiating lines. Their colours are generally pale. I have seen specimens attached to kelp from the Cape of Good Hope, with their parietes white and ribbed, and their radii mottled with pinkish-purple; I have seen other young specimens from the Galapagos Archipelago, of a uniform grayish-blue.

The Scuta generally have their lines of growth moderately prominent; occasionally they are longitudinally striated, with the lines of growth flexuous and upturned at intervals into small, sharp, hood-liked projections, which are symmetrically arranged in straight lines radiating from the apex of the valve; I have seen this structure in some specimens of var. crispatus and in var. occator (Pl. 2, fig. 1 b); and I have noticed an intermediate state in var. communis. The degree to which the basi-tergal corner of the valve is rounded off varies much even in var. communis (Pl. 2, fig. 1 a, 1 d, 1 e). The articular ridge (1 c, 1 e) is broad and much reflexed; and often, but not always, distinctly hooked (1 f). The adductor ridge is confluent with the articular ridge, and runs straight down the valve, bounding the cavity for the depressor muscle; generally the adductor ridge is blunt, and so little prominent as barely to deserve notice; but I have seen it sharp and prominent in one specimen of var. communis, and it is generally prominent in var. coccopoma (1 f), and most remarkably so in var. concinnus (1 g). The cavity for the lateral depressor muscle is generally very slight; but in the two vars. just mentioned, and sometimes in var. communis, it is deep. In var. concinnus (1 g) there is a remarkable plate developed for the attachment of the rostral depressor muscle. The scuta are coloured either dull-purple or reddish, or striped longitudinally white and blue. The surface is sometimes externally depressed in the line of the adductor ridge; and in young specimens there is sometimes, along this line, a chain of pits (1 h), as in full-grown specimens of B. trigonus and lævis.

The Tergum (Pl. 2, figs. 1 i to 1 o) is broad, with a generally closed longitudinal furrow; this furrow is open in young specimens, and it is often, but not always, open in rather large specimens of var. occator; it is always open in var. d’Orbignii (Pl. 2, fig. 1 m), and sometimes in var. concinnus. Apex barely beaked, except in var. spinosus, in which it is sensibly produced. Spur placed either very nearly in the middle of the basal margin, or when least medial, it stands at above its own width from the basi-scutal angle; yet in some specimens of var. occator the spur is less than its own width from this angle. The basal margin (1 i), on opposite sides of the spur, either forms a nearly straight line, or the scutal portion descends lower than the carinal portion, and curves very regularly towards the spur; this is the case in var. d’Orbignii (1 n), and in some specimens of var. occator. The carinal half of the basal margin generally forms an angle with the spur of only a little above a rectangle. The spur varies a little in length and breadth, but never exceeds one fourth of the greatest breadth of the valve. The scutal margin is broadly inflected, the inflected portion forming either a right angle, or somewhat less than a right angle, with the exterior surface of the valve. Internally the articular ridge is prominent, and is either considerably or slightly curved; it extends down either about half, or three fourths, of the length of the valve. The spur is produced for a considerable distance up the internal surface of the valve as a prominence. The crests for the tergal depressor muscle are very feeble. In one specimen, in which both the shell and operculum had undergone much disintegration, the scuta and terga were calcified together.

Compartments: their exterior appearance has been already described. The parietal tubes are not large; they are generally crossed by transverse septa in their uppermost part; but they are sometimes almost solidly filled up by dark shelly layers. The internal surface of the parietes is more or less plainly ribbed; in old specimens, however, it generally becomes smooth. The radii have their septa denticulated on both sides; and they are porose, that is, the interspaces between the septa are not filled up solidly. The radii generally extend from tip to tip of the adjoining compartments, that is, their summits are parallel to the basis; but in three not common varieties, viz., vars. intermedius, occator, and d’Orbignii (the former of which at least must, without the smallest doubt, be ranked as a mere variety), their summits are oblique. I have occasionally met with specimens of var. communis with oblique radii; and this is not very infrequent in young shells. Exteriorly the radii are generally smooth, but sometimes finely ribbed horizontally, owing to the projection of the septa. The alæ have their sutural edges smooth; their summits are usually parallel to the basis, but they are often much broken; in var. zebra, however, in every specimen which I examined, the summits were oblique. The sheath varies much in colour: in var. occator, and in a less degree in var. intermedius and var. d’Orbignii, the portion lining the rostrum and lateral compartments is much darker than the other parts of the sheath. The Basis generally has a thick, underlying, cancellated layer. Sometimes the basis (Pl. 1, fig. b) is irregularly cup-formed.

Mouth: labrum with four or six minute teeth: mandibles with five graduated teeth; inferior point more or less spinose. Maxillæ, either with or without a small notch, beneath the upper pair of spines; in the lower part there are two spines longer than those immediately above them. Cirri, the first pair has the rami unequal, in the proportion of about 19 segments in the longer ramus, to 16 in the shorter. The segments in the latter have their anterior surfaces very protuberant. The second pair is short, with the anterior surfaces of the segments protuberant. On the thorax (Pl. 25, fig. 1), on each side, at the bases of third pair of cirri, there is a projecting membranous plate fringed with fine bristles. The three posterior pairs have their segments shield-shaped in front, generally bearing four pairs of spines, of which the lower pair is minute; between these pairs there are some minute spines. In some young specimens from the Cape of Good Hope, and in var. concinnus, I found six pairs of spines on the segments of the posterior cirri.

Geographical Distribution.—This species is extremely common over the whole of the warmer seas. It ranges from the Island of Madeira to the Cape of Good Hope, and on the west coast of America, from Monterey, in lat. 37° N., in California, to Peru. It is attached to rocks and sub-littoral shells, to floating timber, to kelp, and to Lepas anatifera. It is attached in wonderful numbers to ships’ bottoms arriving at our ports, from West Africa, the West Indies, the East Indian Archipelago, and China. It is generally associated with B. amphitrite and amaryllis. I have already stated that, on the bottoms of vessels, the different varieties are generally grouped together; and this makes me believe that they are local. In Mr. Stutchbury’s collection there are numerous specimens taken from a ship which first went to the west coast of Africa for guano, and then to Patagonia for the same object, and it was interesting to see the manner in which numbers of B. psittacus, a Patagonian species, had become attached on the African B. tintinnabulum. The varieties from the west coast of America seem eminently peculiar; we there find var. coccopoma and concinnus; and a blueish, rugged variety, with peculiar opercular valves.

Geological History.—I have seen specimens in Mr. S. Wood’s collection from the Red Crag of England, which, though not accompanied by opercular valves, I cannot doubt belong to this species. The specimens named by Mr. Sowerby, in the ‘Mineral Conchology,’ as B. crassus, and which I have seen through the kindness of Mr. J. de C. Sowerby, also belong to this species. I further believe that a specimen in Sir C. Lyell’s collection, given to him by M. Dujardin under the name of B. fasciatus from Touraine, is likewise B. tintinnabulum.

Varieties.

With respect to var. communis, I have nothing to remark. The second, var. vesiculosus (Pl. 2, fig. 1 h), is confined to young specimens, and may, perhaps, be due to a want of calcareous matter. With respect to var. validus (Pl. 1, figs. 1 c, 1 f infra), I may observe that some of the coarsest and strongest specimens which I have seen were said to have been attached to a surface of iron. I have seen two large lots of var. zebra (1 g), taken by Mr. Stutchbury, from the bottoms of ships, arriving from Bengal and China, and in both cases associated with var. communis, and in one case with var. coccopoma. I at first thought that this variety, zebra, was specifically distinct, but now I feel no doubt, that it is a mere variety; its body was in every respect identical with that of var. communis.

Nor have I any doubt that var. crispatus, of Schröter (Pl. 1, fig. h), is only a variety, although the scuta in some specimens have a peculiar appearance, externally like these valves in var. occator (Pl. 2, fig.1 b): the scutum is here broader and flatter than in var. communis, and the adductor ridge is very feebly developed, but we shall see how variable this ridge is in all the varieties: externally, the sharp, hood-like points formed by the upturned lines of growth, have a very remarkable appearance, from being arranged in quite straight radiating lines. This structure is evidently caused by the same tendency which produces on the walls the sharp, upturned, irregular points; but it is singular that the scuta are smooth in some specimens with very rough parietes; and, on the other hand, bristling with the symmetrically arranged, hood-like projections, in other specimens on which I could with difficulty detect only a few exceedingly minute points on the walls. In var. communis I have seen a few specimens with a slight tendency in the scuta to become striated longitudinally. The tergum in var. crispatus presents no difference from that in var. communis. Some of the roughest and best characterised specimens of var. crispatus appear to have come off copper-sheathed vessels.

I believe var. spinosus of Gmelin (Pl. 1, fig. i), has been correctly considered by me as a variety, but I have unfortunately seen only one set of specimens with their opercular valves preserved: these were attached to Lepas anatifera. The colour of the shell varies from reddish-purple to nearly white; the radii are sometimes quite white; the walls are slightly ribbed. The scuta in the above specimens, externally were smooth; the adductor ridge was rather more distinct from the articular ridge than in any other variety; and the terga rather more plainly beaked. The tubular, up-curved, calcareous spines sometimes occur only on one side of the shell, and often only in the lower part. These spines are often coloured brighter than the walls. Their presence cannot be accounted for (any more than the state of the scuta in the foregoing var. crispatus) by the nature of the surface to which they are attached; for I have seen one set attached to a large rugged specimen of B. tintinnabulum, and another to the very smooth valves of Lepas anatifera. I believe that this form is almost always associated with var. communis, which is an argument that it is only a variety.

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.

Shell dark rose-coloured, sometimes tinged with purple; orifice toothed. Scutum externally very smooth, covered by membrane. Tergum with distinct crests for the depressor muscles.

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.

There can be no doubt that this species is the B. nigrescens in Chenu, who had access to Lamarck’s original specimens; and there can be equally little doubt that it is the B. gigas of Ranzani, collected, during Baudin’s expedition, at King George’s Sound: it is essentially allied to B. psittacus, but in external appearance strikingly resembles some of the varieties of B. tintinnabulum.

General Appearance.—Shape tubulo-conical: walls smooth, sometimes longitudinally ribbed: colour ashy-gray tinged with blue, but many specimens are dark purplish-blue, owing to the disintegration of the outer lamina, and consequent exposure of the almost solidly filled up, dark blueish parietal tubes; on the other hand, some specimens are quite white. Ranzani describes the colour as earthy-violet, which is very characteristic of some of the specimens. The orifice is apt to be rather small, compared to the size of the specimens, and tends to be hexagonal. The radii are often rather narrow. The opercular valves are tinted pale blue. The basal diameter of the largest specimen is two inches, and its height two and a quarter.

The Scuta have their basi-tergal corner much rounded off, as in B. psittacus, so that the tergal margin does not extend more than half down the valve. The surface is somewhat prominent, along a line running from the apex to the point of chief curvature in the basal margin. The surface is not striated. Internally, the articular ridge is little prominent, and not reflexed; the lower end depends as a free, sharp style or point. The adductor ridge is moderately sharp, and stands some little way distant from the articular ridge: it is produced downwards, and forms a moderately deep and large cavity for the depressor muscle; but this cavity is not closed, and does not extend up, as in the two last species, to the apex of the valve.

Terga, narrow, with a sharp, prominent, needle-like beak. Spur, long, narrow, placed at less than its own width from the basi-scutal angle: the basal margin on both sides slopes down to the spur: the scutal margin is not inflected. Internally, the articular ridge is very feebly developed, but extends down close to the basi-scutal angle. On the under surface in the upper part of the valve, there is a short, very slight ridge, extending on the carinal side, near and parallel to the articular ridge; this slight ridge plays an important part, as in the two foregoing species, in the formation of the beak or apex. Crests for the depressor muscle are hardly distinguishable.

The Walls appear to vary in some degree in strength and thickness; as is likewise the case with the opercular valves. In some of the thinner specimens, the parietal tubes are large, and the longitudinal septa are furnished with small, sharp denticula. The tubes are often thickly lined or almost filled up solidly with blue shell; they are not crossed by transverse septa.

The Radii vary in width; externally they are often finely ribbed transversely, at other times they are smooth; their septa are fine and thin, with their delicate denticuli not extending to the outer lamina: they are very porose. The alæ have their summits parallel to the basis; their sutural edges are most finely crenated. The sheath is blueish, excepting the wedge-like portions of the alæ which have been added during the diametric growth, and these are white.

Mouth: labrum without teeth: mandibles with five sharp teeth: maxillæ with the edge straight. Cirri, first pair with the rami very slightly unequal; segments of the shorter ramus and of both rami of the second pair protuberant: posterior cirri with the segments shield-shaped in front, bearing four pairs of spines, of which the upper pair is much longer than the lower pairs; each pair has a small intermediate tuft of minute spines.

6. BALANUS DECORUS. Pl. 2, fig. 6 a, 6 b.

Parietes pale pink; radii rather darker. Scutum with a small articular ridge. Tergum with the longitudinal furrow very shallow and open; basal margin on both sides sloping towards the spur.

Hab.—New Zealand. Mus. Brit., and Flower: attached to shells.

General Appearance.—Shell conical or tubular, with a large rhomboidal orifice; very pale pink, but tinted yellowish from the persistent epidermis, and sometimes faintly striped longitudinally; radii and sheath of rather a darker pink; scuta in themselves white, though lined by purple corium; the carinal half of the tergum pink. Walls extremely smooth. Largest specimen above one inch in basal diameter.

Scuta, with the finest striæ radiating from the apex; growth-ridges moderately prominent; articular ridge small; there is a very slight and blunt adductor ridge: the hollow for the lateral depressor muscle is rather narrow and deep.

Terga, with the apex slightly prominent or beaked; the longitudinal furrow is of very little depth; on its scutal margin there is a narrow, rounded, slightly prominent ridge, which, however, appears more like a furrow than a ridge. Spur moderately long and blunt; placed at half its own width from the basi-scutal angle; the basal margin on both sides of the spur, slopes gently towards it. Internally, the articular ridge is pretty well developed; the scutal margin is not much inflected; the carinal portion of the under surface of the valve is rough; the crests for the carinal depressor muscle are entirely absent.

Compartments.—Walls moderately strong; parietal tubes small, with transverse septa in their upper ends; inner surface of the walls much less strongly ribbed than is usual. Radii broad, with their summits parallel to the basis; their septa are strongly denticulated. Alæ with their summits oblique; their sutural edges are barely crenated. Basis, thin, flat, or cup-formed. Body unknown.

Affinities.—In general appearance this species comes near to B. psittacus; but in all essential characters it comes much closer to the following species, from which, however, it can easily be distinguished by colour, and by the inner lamina of the parietes not being cancellated.

7. BALANUS VINACEUS. Pl. 2, fig. 7 a-7 d.

Shell purplish dark brown: inner lamina of the parietes cancellated. Scutum finely striated longitudinally. Tergum with the longitudinal furrow shallow and open; basal margin on both sides sloping towards the spur.

Hab.—West Coast of South America. Mus. Cuming.

General Appearance.—Shell conical, with a large, rhomboidal orifice; walls rather thin, coloured, together with the radii and operculum, dark purplish-brown; sheath nearly colourless. Walls smooth, slightly irregular, very finely striated longitudinally. Basal diameter of largest specimen .8 of an inch.

Opercular Valves, unusually smooth, that is without prominent growth-ridges. Scuta, finely striated longitudinally, with the sharp striæ closely approximate. The teeth on the occludent margin are sharp, and stand some way apart from each other. Internally, the whole surface is remarkably flat and smooth: the articular ridge is of moderate breadth, and slightly reflexed: there is no adductor ridge, and the oval depression for the lateral depressor muscle is extremely slight. Terga, with the longitudinal furrow very slight; the bottom of this furrow is feebly striated longitudinally, and there is a trace of a fine, rounded ridge on the scutal margin, as in B. decorus. The basal margin slopes on both sides towards the spur, which is of moderate length and breadth, with its lower end truncated and parallel to the carino-basal margin; the spur stands at about once and a half its own width from the basi-scutal angle. Internally, the valve is lined by very dark, purplish-brown corium; the articular ridge is prominent; in the upper part of the valve, parallel to the articular ridge, there are two or three feeble ridges; there are no crests for the tergal depressores.

The Parietes, though moderately thick, yet are light and fragile; the denticuli at the bases of the longitudinal septa are prominent, and those on the adjoining septa are united together, making a network (Pl. 2, fig. 7 d), but the interspaces between them are not filled up by solid calcareous matter (as is the case with every other species of the genus), but are only crossed at successive levels by fine transverse calcareous septa; the internal lamina thus becoming cancellated, and, though thick, fragile. Hence, in a transverse section of the parietes, the ordinary parietal tubes or pores are seen to be lined on their inner sides by five or six rows of very minute pores. I have not seen any other instance of this structure. The internal lamina is ribbed, as usual, on its inner surface, by the projection of the longitudinal septa. The ordinary parietal tubes are open, to nearly the summit of the shell. The radii are rather thin, and unusually fragile; their summits are parallel to the basis: their septa, as seen on the sutural edges, are extremely thin and denticulated on both their upper and lower surfaces, on the side towards the internal lamina: towards the external lamina, the septa are simple, and the small square pores thus formed, are open or not filled up. The alæ have their summits extremely oblique, being added to very little during the diametric growth of the shell; the narrow margin, however, which is thus added, is coloured red, the rest of the sheath being nearly colourless: the sutural edges of the alæ are smooth. The basis has a thick, underlying, finely cancellated layer of shell.

Animal’s body unknown.

A young specimen, .2 of an inch in basal diameter, differed from the above in being of a much paler purplish-brown. This species is distinct from all its congeners, in its peculiar colour, and likewise in the structure of the inner lamina of the parietes. As already stated, it comes nearer to B. decorus than to any other species.

8. BALANUS AJAX. Pl. 3, fig. 1 a-1 d.

BALANUS TINTINNABULUM (var.) Chenu. Illust. Conch., Tab. 2, fig. 8.

Shell globulo-conical, often elongated in the rostro-carinal axis, pale pink, smooth, extremely massive: parietal pores, close to the basal margin, circular and very small. Scutum with the articular ridge broad and reflexed.

Hab.—Philippine Archipelago, attached to Millepora complanata, Mus. Cuming. Mus. Brit. and Stutchbury.

General Appearance.—Shell globulo-convex, sometimes much elongated in its rostro-carinal axis; smooth; walls excessively strong, massive, and heavy. Orifice oval, rather small in proportion to the size of shell, this being chiefly due to the infolding of the upper part of the rostral compartment. Parietes pale pink, feebly tinted with purple: radii either paler, or tinted of a bright chesnut-brown: sheath rich purplish chesnut-brown. Basal diameter of the largest specimen nearly 3-1/2 of an inch; height 2-3/4: another specimen had a basal longitudinal diameter of 2.9 of an inch, and a transverse diameter of only 1.6; this great difference in the two diameters being caused by the prolongation of the basal portion of the rostrum in the line of the branch of the Millepora, to which the shell had adhered; the height of this same specimen was 1.5; and the diameter of the orifice, both transversely and longitudinally, .75 of an inch.

Scuta, broad, feebly tinted with pink; exterior surface rough, with sharp hood-formed projections, arranged in straight lines radiating from the apex; an inflected portion of the valve along the tergal margin is not roughened. Internally (Pl. 3, fig. 1 d), the articular ridge is broad and reflexed. An adductor ridge can hardly be said to exist, but a slight prominence borders the gentle hollow in which the lateral depressor muscle is attached. The basal margin, on its inner face, is slightly toothed. Tergum white, with the narrow part of the valve, on the scutal side of the spur, rough with the little projecting hoods, like those on the scutum; the other and larger half is smooth: spur rather long, narrow, placed at twice its own width from the basi-scutal angle; on the carinal side, about half of the basal margin slopes down towards the spur. The longitudinal furrow is either quite or nearly closed. Internally, the spur is produced upwards on the valve, as a prominence: the articular ridge is not very prominent. There are no crests for the tergal depressor muscle.

Altogether the opercular valves strikingly resemble those of B. tintinnabulum, but all the characters above mentioned have not been observed in any one variety of this species; perhaps var. coccopoma comes nearest, both in the external appearance of the shell and in the structure of the opercular valves, to B. Ajax.

The Compartments are remarkably compact and solid; the parietal tubes are cylindrical and quite minute even close to the basis; they extend, however, nearly up to the top of the shell; the parietal septa at the basis are thick, and with blunt denticuli; the thickness of the walls in the upper part of the shell is excessive; in the lower part, it is also unusually great, owing to the thickness of the inner lamina, and hence the ribs, generally formed by the projection of the longitudinal septa on the inner lamina, are here visible only close to the basis. The radii are rather wide; their summits are parallel to the basis; the septa on their sutural edges are thin, straight, and closely approximate, and most symmetrically furnished with little denticuli of equal sizes on both sides: the interspaces are nearly filled up solidly, but with some pores still left open. In the upper part of the shell, the radii, like the walls, are of extraordinary thickness: the septa are transverse and horizontal, as seen externally by slight variations in the colour of the radii; internally, as seen in a vertical section of the shell, the septa dip inwards at an angle of above 45°. The alæ are thin, and have their summits oblique: their sutural edges are smooth. The pores in the basis are crossed by numerous transverse septa, and there is an underlying cancellated layer: the internal surface is very smooth.

Animal’s body unknown.

The strength of this Balanus is truly remarkable; and when, by repeated blows, a specimen which I was examining at last yielded, the radii broke sooner than separate at their sutures. In most of its characters, this species approaches B. tintinnabulum, and I believe has been included by Chenu as one of its varieties; but it comes almost equally near to B. stultus, to which it is much more closely allied in its habit of being attached to Milleporæ. By a close and unbroken chain of affinities, B. Ajax, through B. stultus, is connected with B. calceolus and its allies in section (B), which live attached to Gorgoniæ. Some of the specimens of B. Ajax, are almost as much elongated in their rostro-carinal axis, as are the species in section (B); and there is an affinity in the same direction in the smallness of the pores in the radii of B. Ajax; indeed, had the basis in this species been generally more boat-or cup-formed, I should have placed it as the first species in section (B), instead of, as at present, the last species in section (A). The intermediateness of the characters of B. Ajax has been one chief cause why I have rejected the genus Conopea, which was instituted by Say for the species living attached to Gorgoniæ.