Part 22

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.

[88] According to the letter of the Rules of the British Association, Ellis's name ought to be retained, as it was published in 1758, the same year during which the 10th edition of the 'Systema Naturæ' appeared, in which edition the binomial method was first used. But as Ellis himself did not then know of, or follow this method, it might be disputed whether, according to the _spirit_ of the law, his name ought to stand. The only other name given to this species is that of _tulipa_, affixed by Poli in 1791, but this name had been previously used by Müller in 1776, and by Chemnitz in 1785, for another species, the _B. Hameri_ of this work; and likewise, also previously to Poli, by Bruguière in 1789, for still another species, viz., _B. tintinnabulum_ of this work: under these complicated causes of confusion, I think it is highly advisable to adopt Ellis's name. I may add that the _B. tulipa_ of Mr. G. B. Sowerby is the _B. tintinnabulum_ of this work. It is possible that the _B. conoides_ of Brown, 'Illustrations Conch.' (1st edit. pl. 6, fig. 7), may be our present species; but without details of structure it is hardly possible to identify, in many cases, the species of Balanus.

_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.