Section C.

Parietes and basis permeated by pores. Radii not permeated by pores.

14. BALANUS TRIGONUS. Pl. 3, fig. 7 a-7 f.

Parietes ribbed, mottled purplish-red; orifice broad, trigonal, hardly toothed. Scutum thick, with from one to six longitudinal rows of little pits. Tergum without a longitudinal furrow; spur truncated, fully one third of width of valve.

Hab.—Java; East-Indian Archipelago; Peru; West Columbia; California; Sydney; New Zealand. Mus. Brit., Cuming, Stutchbury, Dunker, &c.

General Appearance.—Shell conical, generally depressed; orifice broad, triangular, almost equilateral; walls coloured or only mottled with purplish-pink, having either irregularly branching, or regular, longitudinal ribs, which are generally white. The radii are pale pink, or nearly white: the opercular valves have either their upper parts, or nearly their whole surface, clouded with pinkish-purple: the epidermis is not persistent: the walls are moderately strong: the largest specimen was one inch, but generally full-grown specimens are about half an inch in basal diameter.

The Scuta have the lines of growth highly prominent. From one to five or six rows (7 b, 7 c) of nearly circular, or transversely oblong, deep pits, extend down the middle of the valve; rarely there is not even one row; in this latter case, the valve is not striated longitudinally. These little pits are caused by one or more deep longitudinal furrows, crossed by the lines, or rather ridges, of growth. In the same group of specimens, I have seen individuals with three, five, and six rows; and even a few specimens with only one row, or none at all. The outline of the valve is elongated, with the apex slightly reflexed: the inner surface is protuberant, sometimes to a remarkable, but variable degree. The articular ridge is not very prominent, but it extends fully half-way down the valve, and generally ends in a small free point. There is a short adductor ridge, and a deep narrow pit or cleft for the lateral-depressor muscle. Terga, externally smooth, flat, with scarcely a trace of a longitudinal furrow; spur broad (7 e, 7 f), varying from half to one third of the width of the valve, with the end truncated, situated either near or quite close to the basi-scutal angle. The crests for the depressor muscles are moderately well developed.

Compartments.—The parietal tubes are, in their upper parts, filled up solidly, without transverse septa. The radii generally have their summits slightly oblique, and this is almost always the case with the radii of the rostrum; the other radii sometimes extend from tip to tip of the parietes, and are parallel to the basis; rarely the radii are considerably oblique. The septa of the radii are very obscurely denticulated, and the interspaces between them are filled up solidly. The alæ have their sutural edges thin and smooth.

Mouth.—Labrum with three teeth close together on each side of the central notch: mandibles with four teeth, the fourth being small, the fifth either absent or scarcely distinguishable from the inferior angle: maxillæ without any notch, with the two lower spines rather longer than the others. Cirri: In the first pair, one ramus is only half the length of the other; in the second pair, both rami are short and about equal in length; in the posterior pairs, the segments, which are not protuberant, bear four pairs of spines, of which the three lower pairs are short.

This species is widely-distributed, and where found seems to be common. It is generally attached to shells of mollusca, but I have seen it also attached to wood. I have found it associated with B. tintinnabulum, var. concinnus, and coccopoma, with B. psittacus, improvisus and amphitrite, and with Elminius modestus.

Young specimens bear a considerable resemblance to certain young varieties of B. tintinnabulum, and can indeed be distinguished from them only by a careful examination of the opercular valves; for it should be borne in mind, that in certain cases the scuta in B. tintinnabulum are pitted with little cavities. This species in some respects is, I think, allied to B. porcatus, but it is far more closely related to B. spongicola, and can be discriminated with difficulty from certain varieties of this latter species. In Mr. Cuming’s collection, there is a group of small specimens, crowded between some older specimens, which are remarkable from the shell being oval in a transverse section,—from the smoothness of the walls,—and from the absence of pits on the scuta; yet there could be no doubt that these specimens belonged to our present species.

15. BALANUS SPONGICOLA. Pl. 4, fig. 1 a-1 d.

BALANUS SPONGICOLA. Brown’s Illustrations of the Conchology of Great Britain (1827), pl. 7, fig. 6: 2d edit. (1844), pl. 53, figs. 14-16.

Parietes generally smooth, sometimes longitudinally folded; coloured pink: orifice toothed. Scutum longitudinally striated. Tergum, with the apex produced, without a longitudinal furrow; spur truncated, about one third of width of valve.

Var. with the walls slightly folded longitudinally.

Hab.—South coast of England, and Tenby in South Wales, often imbedded in sponges; attached also to shells and rocks in deep water; Mus. Brit., Jeffreys. Algiers, on Mytili and Serpulæ, with B. perforatus, Mus. Mac Andrew. Madeira, with B. tulipiformis, Mus. Lowe. Lagulhas Bank, Cape of Good Hope, on detached kelp, with B. Capensis, Mus. Sir J. Ross. Imbedded in sponge with Acasta spongites, Mus. Bowerbank. Var. West Indies.

Fossil in Coralline Crag, Mus. S. Wood.

General Description.—Shell tubulo-conical; orifice of moderate size, rather deeply toothed; colour dull pink, or purplish, or dark flesh-colour; sometimes the radii are paler, sometimes of the same colour with the parietes. Surface smooth when well preserved, having transverse rows of minute spines. In the West Indian variety the walls are slightly or much folded, but I will describe this form separately. Size of largest specimen (Mus. Jeffreys), .6 of an inch in basal diameter.

Scutum, with fine ridges radiating from the apex, and with the lines of growth, crenated: internally, the articular ridge is small, adductor ridge short and barely distinct: there is a rather deep and narrow pit for the lateral depressor muscle. The whole valve is much thinner than in B. trigonus, which in most respects it closely resembles. Tergum, with the apex pinkish purple, produced or beaked, but the beak is not needle-like, as in B. psittacus and its allies, for the carinal margin is perfectly preserved up to the tip. Externally the valve is nearly flat, for the longitudinal furrow is very shallow. The spur is about one third of the width of the valve; its lower end is abruptly truncated: in European specimens (1 b) the whole basal margin, on the carinal side, slopes down to the spur in a straight line, which, together with the sharpness and production of the basi-scutal angle of the spur itself, gives to the whole valve a peculiar appearance: in the specimen (1 c) from the Lagulhas Bank, the basal margin on the carinal side is a little more hollowed out, but it is quite impossible to doubt about the specific identity of these specimens: in the West Indian variety (1 d) the basal margin on the carinal side forms a distinct but obtuse angle with the spur. In all cases the crests for the depressor muscles are very feebly developed.

The Compartments have their radii developed to a rather varying degree, with their summits oblique; hence the orifice is toothed: the sutural edges of the radii have their septa barely denticulated; the sutural edges of the alæ are smooth. The basis, as with the other species of this section, is permeated by pores; yet I found one specimen, from the Cape of Good Hope, with the basis apparently solid, thus offering a very singular anomaly. In the specimen imbedded in sponge, the basis, as viewed externally, is concave; whereas in Acasta, which always inhabits sponges, the basis is highly convex or hemispherical.

The Mouth and Cirri resemble those of B. trigonus, and I can point out no distinguishing character.

With respect to the variety from the West Indies, I have seen two sets of specimens differing somewhat in external appearance, one set attached to a coral from St. Vincent’s, and another set to an Avicula from an unknown locality; at first I described these specimens, with some hesitation, as a distinct species, and I am very far from sure whether this would not have been the more correct course, although I am unable to point out any sufficient diagnostic characters. This form differs from the ordinary B. spongicola, in the walls being more rugged, stronger, and slightly or deeply folded longitudinally; in this latter case the shell in external aspect differs much from ordinary specimens of B. spongicola; but this is a variation so common that I dare not place any reliance on it. The colour is more purple; the summits of the radii perhaps rather less oblique. In the scuta the only difference is that the articular ridge seems rather longer, and the adductor ridge perhaps more prominent: in the terga, as already remarked, the basal margin on the carinal side does not slope so straight into the spur. These differences I consider all too slight to be of specific value. The difficulty in determining the nature of this variety is added to by its approach to B. trigonus in all those points in which it departs from the ordinary B. spongicola, so that for a short time I was even tempted to consider both these species as varieties of one form. But until B. trigonus is found with its scutum longitudinally striated, and with its tergum beaked, it can hardly be confounded with B. spongicola; for it should be observed that when in B. trigonus the rows of little pits disappear from the scuta, as sometimes happens, though rarely, yet these valves do not become longitudinally striated.

Balanus spongicola occurs, mingled with B. tulipiformis, in the Mediterranean, and by the external characters of the shell alone cannot be distinguished from that species; but the striated scuta and beaked terga suffice to separate them. Again, this species, at the Cape of Good Hope, occurs mingled with B. Capensis, and from the non-striped young varieties of that species, it can, externally, be distinguished only by the beak of the tergum not being sharp like a needle. I have seen a single, perfectly characterised specimen, with its opercular valves preserved, found by Mr. S. Wood in the Coralline Crag at Sutton, mingled with B. inclusus.

16. BALANUS LÆVIS. Pl. 4, fig. 2-2 g.

BALANUS LÆVIS. Bruguière. Encyclop. Meth. (1789), Pl. 164, fig. 1.[91]

------ DISCORS. Ranzani. Mem. di Storia Nat., 1820, Tab. 3, figs. 9 to 13.

------ COQUIMBENSIS. G. B. Sowerby, in Darwin’s Geology of South America (1846), Tab. 11, fig. 7.

Shell covered by brown membrane, or naked and white or pale purple; orifice small; radii very narrow. Scutum with one or two deep longitudinal furrows.

Var. nitidus (fig. 2): shell not covered by membrane, white or pale purple: orifice but slightly toothed: scutum generally with two furrows. Hab.—Chile, as far south as Concepcion; Peru; California.

Var. Coquimbensis (fig. 2 a): with the basal cup partly filled up with thin, irregular, calcareous layers, making a cancellated mass. Fossil, and recent.

Hab.—Strait of Magellan, ten to twenty fathoms, attached to shells; often entirely surrounding pebbles, forming globular masses; associated with Verruca lævigata. Chile and Peru, (generally var. nitidus), often attached to Balanus psittacus. California. Very common.

Fossil in an ancient tertiary formation (middle bed) at Coquimbo, Chile. In a recent deposit (var. nitidus) at the height of 1000 feet at Valparaiso; with Human remains at San Lorenzo, Callao, Peru.

I may premise that, having myself collected this species from the same locality, the Strait of Magellan, where no allied species occurs, attached to the same Mytilus and associated with the same Verruca, I feel confident that it is the B. lævis described by Bruguière; and there can hardly be any doubt that it is the B. discors of Ranzani. With respect to the old tertiary specimens from Coquimbo, named B. Coquimbensis by Sowerby, they differ from the recent in no respect, except in being considerably larger; and therefore I cannot consider them specifically distinct. At first I was unwilling to believe that the specimens with a single very broad longitudinal furrow, and those with two rather broad, or with one narrow furrow, on their scuta, could belong to the same species; but I soon found that all these varieties occurred mingled together, and that they differed in no other respect whatever. Generally, however, all the individuals in the same cluster had the same variety of scutum,—thus adding one more to the many instances amongst cirripedes of variations common to whole groups of specimens. Still more unwilling was I to believe that var. nitidus and the common variety could belong to the same species. Their general aspect is totally unlike: var. nitidus has a smooth, clean, naked shell, either white or pale purple, somewhat globulo-conical, often with a nearly entire orifice; whereas the other common variety generally has a more steeply conical shell, with a toothed orifice, and is covered by a dirty brownish membrane. Moreover, though I have seen hundreds of specimens from Tierra del Fuego, I have not seen one specimen of var. nitidus, or even of an approach to it in appearance; and, on the other hand, var. nitidus is the common form in Chile and Peru; though I have seen one or two specimens of the membrane-covered variety from Valparaiso. Such facts strongly induced me to believe that these forms were specifically distinct; but upon careful examination I could find no other or more important differences than those just specified. Some specimens from northern Chile are in an intermediate condition; and from Concepcion, in the south of Chile, where the climate approaches in character to that of the more southern parts of the Continent, there are many specimens, in so intermediate a condition that I know not whether or no to rank them under var. nitidus. Thus I became convinced that these forms are only varieties. At Concepcion, some few specimens are pale purple, and yet are wholly invested by thick brown membrane, thus uniting the two extreme varieties. From California I have seen both varieties, but I do not know which is most common there. With respect to the great difference in aspect between the specimens from northern Chile and Tierra del Fuego, we shall hereafter see a strictly analogous case in Balanus flosculus. Finally, I may add that B. lævis seems to represent in the southern hemisphere and on the west coast of North America, the B. perforatus of Europe and Western Africa.

General Appearance.—Shell conical, sometimes slightly globular; surface smooth (that is, not folded), either naked, and in that case white or pale purple, or covered by dirty yellowish-brown membrane. Orifice small, more or less toothed, rarely exceeding one third of the basal diameter. Radii very narrow, often not developed, the six sutures forming in all cases deep and narrow clefts. The largest recent, but much depressed, specimen which I have seen (from the Strait of Magellan) was three fourths of an inch in basal diameter; specimens growing congregated are often much elongated. I have seen one with the basal cup between two and three times as deep as the height of the compartments. Of the ancient tertiary specimens, the largest had a diameter of three fourths of an inch, and a total length of actually two inches (fig. 2 a); another of these fossils had a basal cup in depth equalling four fifths of the entire length of the shell and basis.

The scutum has either one very broad and deep longitudinal furrow (2 b), or two moderately broad and deep (2 e), or two narrow and deep, or less frequently one narrow and inconspicuous longitudinal furrow (2 f); rarely there is not one furrow; sometimes there are none towards the apex, whilst furrows have been formed in the lower part of the valve. In young specimens the furrows extend down to the actual basal margin, but in old specimens they often fall short of this, and, as a consequence, the furrows become crossed by one, two, or three calcareous ridges, which ridges at successive periods formed the basal margin of the valve. The external surface is covered by yellow membrane; and fragments of several successive opercular membranes are often attached to the zones of growth.

Internally the articular ridge is not very prominent, but is remarkable (2 c, 2 d) from its lower point being produced into a long, sharp, sub-cylindrical, free style (like the hinge of a common gate), which is generally broken off in disarticulating the valve from the tergum. The adductor ridge is either sharp and prominent or blunt: it extends up the middle of the valve nearly to the apex, and downwards it trends a little towards the occludent margin. The pit for the lateral depressor muscle is minute but deep: the basal margin is sometimes hollowed out under this pit. Sometimes there is a distinct, but blunt ridge, caused by one of the furrows outside, parallel to the adductor ridge, and placed between it and the little pit for the lateral depressor; in this case, the basal margin, as viewed internally, is rendered sinuous (2 d), as is best exhibited in the great fossil specimens from Coquimbo.

Tergum (2 g).—Spur of moderate length and breadth, with its lower end obliquely truncated and rounded. The longitudinal furrow has its edges somewhat folded in. The basal margin on the carinal side of the spur is sometimes a little hollowed out. The crests for the depressor muscles are well developed; but the corner of the valve supporting them is extremely thin, and is often imperfectly calcified.

Compartments.—The parietal tubes are not crossed by transverse septa, but in their upper parts are filled up solidly. The radii are always very narrow, with their summits oblique, though to a variable degree: their sutural edges have fine and closely approximate septa, with minute denticuli: the sutural edges are received in a furrow, on the opposed compartment, of unusual depth; hence the lines of suture run, in the lower part of the shell, almost exactly in the middle between each two compartments. The alæ are added to above the level of the opercular membrane.

The Basis is often thick, with an underlying layer, largely cancellated or honeycombed. When many specimens grow crowded together, the basis is generally deeply cup-formed, or even sub-cylindrical; and equals as much as four fifths of the length of the entire shell. In such cases, in some few recent specimens, and in all the large or even quarter-grown old tertiary specimens, but not in the quite young fossil specimens, a structure is presented, which I have not seen in any other Cirripede, namely, the basis (Pl. 4, fig. 2 a) is filled up for one third, or even for more than half its depth, by successive, separate, calcareous, transverse layers or septa. It would appear as if the basal cup had grown too large for the animal’s body, and so required filling up. The layers are thin and fragile; a single layer never stretches across the whole shell; each is irregularly mammillated or blistered, with the convex surfaces generally directed upwards; the layers are furnished on their under sides with little pillars and short ridges, resting on the layers beneath; it rarely happens that the supports of one layer lie directly over those of another, though this is sometimes the case. In a vertical section, the mass formed by these irregular layers has a coarsely cancellated structure. This structure, although confined to this one Cirripede, is not so anomalous as might at first be thought, for in most species of the genus, each time that the circumference of the basis is added to, an excessively thin calcified film is thrown down over its whole inner surface; and in any of these species, if the films had been formed thicker and had rested only on certain points, instead of over the whole underlying layer, the cancellated structure above described would have been produced.

Mouth: the labrum is either destitute of teeth, or has two or three very minute teeth. The palpi have a tuft of very long spines at their ends. The third tooth of the mandibles is thicker and larger than the two upper ones. The maxillæ have either a nearly straight edge, or the inferior corner is obliquely truncated, and projects much beyond the rest of the edge. In the Cirri, none of the segments are very protuberant: in the first pair, one ramus is nearly twice as long as the other: in the posterior pairs, the segments are not much elongated, but each supports seven pairs of spines.

Var. nitidus: with respect to this variety I have little to add to my preliminary remarks on its peculiar appearance, owing to its smooth, naked condition, and pure white or pale purple colour. This colour, when examined through a lens, is seen to consist of very fine longitudinal stripes; and is produced by the calcareous matter within the longitudinal parietal pores being thus coloured. Generally the scuta have two longitudinal furrows; but I have seen a scutum of one perfectly characterised specimen with only a single broad furrow, like that which frequently occurs in the membrane-covered variety. Var. Coquimbensis, as before stated, differs only in its greater size: the scutum, in the one specimen examined, had two broad longitudinal furrows; neither it, nor the tergum differed from certain varieties now found on the coast of Chile.

17. BALANUS PERFORATUS. Pl. 5, fig. 1 a-1 d; Pl. 4, fig. 3 a-3 c.

BALANUS PERFORATUS. Bruguière. Encyclop. Meth., 1789, Tab. 164, fig. 12 infra.

LEPAS ANGUSTA. Gmelin. Syst. Naturæ, 1789.

---- ORE ANGUSTIORE. Chemnitz. Vol. viii, Tab. 98, fig. 835.

BALANUS CORNUBIENSIS CONICO ORE MINORE. Ellis. Phil. Trans. vol. 50, 1758, Tab. 34, fig. 16.

LEPAS BALANUS ET FISTULOSUS. Poli. Test. Siciliæ (1795), Tab. 4, fig. 5, Tab. 6, fig. 1.

BALANUS COMMUNIS. Pulteney. Dorset Catalogue, 1799.

------ ---- Montagu. Test. Brit., 1803.

LEPAS ANGUSTATA. Wood. General Conchology, 1815, Pl. 6, fig. 5.

BALANUS CRANCHII. Leach (!). (B. Blainvillii in Tab.) Encyclop. Brit. Suppl., vol. iii, 1824.

------ ---- Brown. Illust. Conch., 1827, Pl. 7, fig. 9, 10, and 2d Edit., Pl. 53, fig. 9-12.

------ PERFORATUS. Chenu. Illust. Conch., Tab. 3, fig. 9, Tab. 6, fig. 15.[92]

Shell pale purple, or white, or dirty ash-colour; smooth, or, from being corroded, finely ribbed longitudinally; sheath purple; orifice generally small; radii generally narrow or absent. Scutum, internally, with a short minute ridge, parallel and close under the prominent adductor ridge. Tergum with the apex somewhat produced.

Var. angustus (Gmelin) Pl. 5, fig. 1 a: pale dull purple or white; orifice small or of moderate size; radii very narrow or moderately wide, white or pale purple, with oblique summits.

Var. Cranchii (Leach) Pl. 5, fig. 1 b: corroded, covered with fine longitudinal ridges owing to the exposed, filled-up, parietal tubes; dark dirty ash-colour, with a tinge of purple: radii not developed, or very narrow with oblique summits; orifice small.

Var. fistulosus (Poli) Pl. 5, fig. 1 d: shell cylindrical, white or dull purple; orifice of moderate size or small; basis deeply cup-formed.

Var. mirabilis, Pl. 5, fig. 1 c: bright purple; radii white, very broad, with their summits parallel to the basis; orifice entire, large.

Hab.—Southern shores of England; South Wales; Mediterranean; Western Africa, southward to Loanda, in 9° S.; West Indies (?). Generally adhering to rocks at a low tidal level; in one case attached to the floating Lepas Hillii, Mus. Jeffreys.

This is a well-marked species, and in its essential characters does not vary much; but owing to the shell being almost as often white as purple,—to its being remarkably subject to disintegration,—to its often becoming cylindrical,—to the radii being either not at all, or slightly, or moderately, or largely developed, and consequently to the orifice of the shell varying in size, the general external appearance of the different varieties is singularly diversified; but when a series of specimens is examined, it is easy to see how one form passes into another.

General Appearance.—Shell conical, with the orifice oval, unusually small, being generally only from one third to half of the basal diameter; sometimes moderately large; in one single instance as wide as the basis. Radii, often represented by mere lineal fissures, or they are narrow, or sometimes moderately wide. Colour pale, dull purple, sometimes lilac, often passing into a dead pure white: the same individual will occasionally have one part of its shell white, and another purple: the purple tint almost invariably is nearly uniform, or not in stripes. The radii are generally white, when the whole shell is purple, but sometimes they are pale purple: the sheath is apparently always coloured of a fine claret-purple, with the triangular portion of the alæ, added during diametric growth, generally white, but sometimes purple. The surface is quite smooth, but very often, especially on the shores of England, whole groups of specimens (excepting the very young ones,) have had the outer lamina of the parietes entirely corroded and removed; in this case the shell assumes a dirty, more or less dark, ash-colour, feebly tinted with purple, and the whole surface, owing to the exposure of the solidly filled-up parietal tubes, becomes finely striated, or covered with very narrow, longitudinal ridges. When specimens are crowded together they often become cylindrical, and much elongated, owing to the basis becoming deeply cup-formed: I have seen specimens, half an inch in diameter in the widest part, one inch and a half in height, the walls forming only a third of this. The largest specimen which I have seen (from the southern shores of England) had a basal diameter of 1.2 of an inch; some very steeply conical specimens were .9 of an inch in height, and .8 in basal diameter.

Scuta, externally, slightly convex; growth-ridges approximate, moderately prominent. Internally (Pl. 4, fig. 3 a) the articular ridge is moderately developed, with the lower end produced downwards into a freely depending, flattened style, somewhat variable in size, but not so long as in B. lævis, and easily broken in disarticulating the valves. The adductor ridge is very prominent, running from almost the apex of the valve, close to the articular ridge, to near the basal margin. The basi-tergal portion of the valve is converted by the adductor ridge into a rather deep cavity, within which there is a short, sharp, and minute ridge, close and parallel to the adductor ridge, and bounding the impression left by the lateral depressor muscle: this insignificant ridge was present in every specimen; it occurs only in very few other species, as in B. nubilus and cariosus. The thickness of the valve sometimes varies a little, and when thick the adductor ridge does not appear quite so prominent. Tergum, with the apex moderately beaked and produced; beak triangular in section, coloured dark purple, as is the upper internal surface of the valve; the longitudinal furrow is deep, and has its edges folded in, and even quite closed. The spur is moderately long and narrow; but its width varies a little (Pl. 4, fig. 3 b, 3 c), and consequently it stands at either rather above or at twice its own breadth from the basi-scutal angle: its lower end is either bluntly pointed or square, and generally is feebly toothed on the under-side. The basal margin of the valve generally slopes a little, on both sides, towards the spur. Internally, the scutal margin is but slightly inflected: the articular ridge is but slightly prominent, and but little curved; in the upper part of the valve there are generally several very minute ridges, parallel to the articular ridge, on the side towards the scutum. The internal surface of the spur itself is sometimes concave. The crests for the carinal depressor muscle are barely developed. It may here be mentioned that on the opercular membrane many long spines stand rudely arranged in rows.

Parietes: the parietal tubes have not transverse septa; but are solidly filled up in their upper parts by dark-purple layers of shell. The radii, as already stated, are either not at all developed, or are extremely or only moderately narrow, with their summits more or less oblique: in Mr. Cuming’s collection, however, there is an unique specimen, var. mirabilis (Pl. 5, fig. 1 c) with the aperture of the shell as wide as the basis, with bright purple parietes, and white, very broad radii, having their summits parallel to the basis. The septa of the radii are finely denticulated, and the interspaces are filled up solidly. The alæ have very oblique summits, and their edges are finely crenated. Basis, flat, or deeply cup-shaped; there is often an underlying, coarsely-cancellated layer.

Mouth: labrum finely hairy, but without any teeth; mandibles, with the 4th tooth small; the 5th confluent, with the sometimes smooth, sometimes pectinated inferior angle. Maxillæ, rather broad, with a slight notch under the upper pair of spines. Cirri, first pair, with one ramus, having 29 segments, and above one third longer than the shorter ramus, having 17 segments; these latter segments are remarkable by the extent to which their upper front surfaces are laterally produced into projections, twice as long as the breadth of that portion of the segment which is articulated to the adjoining segment. These projections have a double row of serrated spines on their upper edge, and a beautiful radiating bundle at the end; the projections decrease in length, both in the upper and lower segments. The second cirrus (Pl. 29, fig. 4) has the segments (13 in number, in the same individual with the segments above enumerated) of both rami produced in the same singular manner as in the first pair. The third pair have only inverted conical segments, coloured darker purple than the other cirri. The sixth pair had in the same individual 31 or 32 segments, and therefore one or two more than in the longer ramus of the first pair.[93] The segments in the posterior cirri have their anterior faces shield-shaped, and bear 6 or 7 pairs of spines, with some minute intermediate spines. There is the usual point at the dorsal basis of the penis.

Range.—This species is common on the southern shores of England and in the Channel Islands: the largest specimens which I have seen came from these quarters. The most northern point whence I have seen specimens, is Tenby, in South Wales. This species is common throughout the Mediterranean; I have seen specimens from Malaga, Sicily, Algiers, and Smyrna; thence it ranges down the western coast of Africa, as far south as the Gambia and Loanda, in 9° south latitude. I believe British specimens are more often corroded than those from further south. Amongst some old, ill-kept specimens in a box in the British Museum, marked “Kingston, Jamaica,” there were some of this species: also I received some specimens, marked “S. America,” from Mr. G. B. Sowerby: again, Ellis, in Phil. Trans., vol. 50, part 11, gives a figure (Tab. 34, fig. 15) of some specimens from the West Indies, which I believe to be B. perforatus: hence, it is in some degree probable that this species, like B. tintinnabulum, and amphitrite, and improvisus, may be found on both sides of the equatorial Atlantic. Balanus perforatus is attached, together with B. tulipiformis, trigonus, amphitrite, Chthamalus stellatus, and Pollicipes cornucopia, usually to rocks, near the lower limit of the tidal level; but I believe, from specimens kindly sent me by Mr. Mac Andrew, that it is frequently obtained by dredging; one specimen was even marked 30 fathoms. According to Poli, it is sometimes attached to the bottoms of vessels; and I have seen a specimen adhering to the floating Lepas Hillii.

Affinities.—This is a distinct species, closely allied to no other species, but comes nearest to B. lævis, which is its representative in Southern America, and on the whole west coast of that continent. It is allied to that species, and differs from most other species, in the general form of the shell, its small orifice, narrow radii, and often deeply cup-formed basis. It agrees to a certain extent in the colouring, though the purple here is much more prevalent, and is not confined to the shelly matter filling up the parietal tubes. It agrees with that species in the general structure of the scutum; but the two or three deep, longitudinal furrows are here absent; and the minute ridge, parallel to and almost under the adductor ridge, is a peculiarity confined to this and very few species in the genus. The terga differ from those of B. lævis, chiefly in the spur being narrower, and in the apex being beaked. Lastly, the highly protuberant segments of the one ramus in the first cirrus, and of both rami in the second pair, are here remarkable. With regard to the varieties, I have nothing to add to their short diagnostic characters above given.

18. BALANUS CONCAVUS. Pl. 4, fig. 4 a-4 e.

BALANUS CONCAVUS. Bronn. Italiens Tertiär-Gebilde (1831) et Lethæa Geognostica, b. ii, s. 1155 (1838), Tab. 36, fig. 12.[94]

------ CYLINDRACEUS, var. c. Lamarck. Animaux sans Vertèbres (1818).

LEPAS TINTINNABULUM. Brocchi. Conchologia Sub-Appen., t. ii, p. 597 (1814).

Shell longitudinally striped with white and pink; or dull purple; sometimes wholly white. Scutum finely striated longitudinally; internally, adductor ridge very or moderately prominent.

Hab.—Panama; Peru; S. Pedro in California; Philippine Archipelago; Australia. Mus. Brit., Cuming, Stutchbury, Aug. Gould.

Fossil in Coralline Crag, England; Mus. Brit., S. Wood, Bowerbank, Lyell, J. de C. Sowerby, Tennant. Sub-Appennine formations, near Turin, Asti, Colle in Tuscany, Mus. Greenough, &c. Tertiary beds, near Lisbon, Mus. D. Sharpe and Smith. Bordeaux (?) Mus. Lyell. Tertiary beds, Williamsburg; and Evergreen, Virginia, Mus. Lyell. Maryland, Mus. Krantz. Recent formations[95] near Callao, Peru, Mus. Darwin. Red Crag (Sutton) Mus. S. Wood.

This species has caused me much trouble. Looking first to the recent specimens, I examined several from Panama and California, which, though differing greatly in colour, resembled each other in their scuta having the adductor ridge extremely prominent, and in having (Pl. 4, fig. 4 a), an almost tubular cavity for the attachment of the lateral depressor muscle,—characters which at first appeared of high specific value; but I soon found other specimens from Panama in which these peculiarities were barely developed. I then examined a single specimen from the Philippine Archipelago, resembling in external appearance one of the Panama varieties, but differing in the scuta being externally strongly denticulated in lines instead of being merely striated,—in the adductor ridge being far less prominent,—and in the spur of the tergum being broader and more truncated; I therefore considered this as a distinct species. I then examined a single white rugged specimen from the coast of Peru, which differed from the Philippine specimen in the shape of the well-defined denticulations on the scuta, and in some other trifling respects, and in the segments of the posterior cirri bearing a greater number of spines; with considerable doubt, I also named this as distinct. But when I came to examine a large series of fossil specimens from the Coralline Crag of England, from northern Italy, from Portugal, and from the southern United States, I at once discovered that the form of the denticuli on the scuta was a quite worthless character,—that in young specimens the scuta were only striated,—that the prominence of the adductor scutorum ridge and the depth of the cavity for the lateral depressor muscle varied much (as in the case of the recent specimens), owing apparently to the varying thickness of the valve,—that in the terga the spur varied considerably in length and breadth, the latter character being in part determined by the varying extent to which the edges of the longitudinal furrow are folded in,—and lastly, that in young specimens the basal end of the spur is much more abruptly truncated than in the old. Hence I have been compelled to throw all these forms, originally considered by me as specifically distinct, into one species. I must repeat that this considerable variation in the prominence of the adductor ridge, and in the depth of the pit for the lateral depressor muscle—the pit in some cases becoming even tubular—is a very unusual circumstance.

With respect to the fossil specimens[96] from the above-stated several distant localities, I consider them as certainly belonging to one species, though varying considerably in several points of structure. When compared with the recent specimens, they differ from them in often attaining a considerably larger size; in the parietes being often, but not always, longitudinally ribbed; and in the radii often having more oblique summits. On the other hand, considering the many points of identity between the fossil and the recent specimen, I have concluded, without much doubt, that they ought all to be classed together. I may remark that, in the Coralline Crag specimens, the spur of the tergum (Pl. 4, fig. 4 d), is unusually long and narrow; it is broader and shorter in the Italian specimens (4 e), and variable in this respect, in the United States specimens; the scuta of the Lisbon specimens are remarkable for the greater prominence of the adductor ridge, and for the depth of the lateral depressor cavity. Some of the specimens from all the several localities are identical with the recent ones from the coast of Peru. The walls of the shell in the Coralline Crag specimens, are generally ribbed longitudinally. I have entered into the above particulars, on account of, in the first place, its offering an excellent example how hopeless it is in most cases to make out the species of this difficult genus without a large series of specimens; secondly, as showing how the characters alter with age; and thirdly, as a good instance of the amount of variation which seems especially to occur in most of the species which have very extensive ranges.

Some of the pink-striped Panama varieties, though having a somewhat different aspect, can be distinguished from certain varieties of B. amphitrite only by their scuta being longitudinally striated,—a character in this species variable in degree, and in most cases of very little value. Some of the other recent varieties are sufficiently distinct from B. amphitrite; and the great fossil Coralline Crag specimens, which stand at the opposite end of the series of varieties, with their ribbed walls, very oblique radii, and coarsely striated scuta, are extremely unlike B. amphitrite. With respect to the nomenclature of the present species, I have little doubt that I have properly identified the Italian fossil specimens with B. concavus of Bronn, who has given a very good figure of this species in his ‘Lethæa Geognostica;’ it must, however, be confessed that the longitudinal striæ on the scuta are not there represented. Considering the large size and frequency of this species in Europe and in the United States, it has probably received several other names, besides the two incorrect synonyms, quoted at the head of this description. I should add that the true B. cylindraceus (not var. C) of Lamarck, according to the plate given by Chenu in his ‘Illust. Conch.,’ is the B. psittacus of South America. I have seen in collections specimens of B. concavus labelled as B. tulipa of Poli (B. tulipiformis of this work),—a very natural mistake, without the opercular valves be carefully examined.

General Appearance.—Shell conical, often steeply conical; orifice rather small, with the radii narrow, and generally in the fossil specimens very oblique; surface generally smooth, sometimes rugged, and in the coralline crag specimens generally ribbed longitudinally, the ribs being narrow. Colour various, either dull reddish-purple with narrow nearly white, or wider dark longitudinal bands; or, again, pale rosy-pink with broad white bands; or lastly, wholly white. The radii are either darker or paler than the parietes. The opercular valves are either dark purple or nearly white. Pale pink and white stripes are visible on some of the Italian and Portuguese tertiary specimens; and in most of the fossils the sheath is tinged dull red.

Dimensions.—The largest actually recent specimen which I have seen, from the Philippine Archipelago, had a basal diameter of 1.2 of an inch; the Peruvian pleistocene specimen is 1.7 in diameter; specimens from the crag and from the Italian deposits, however, sometimes slightly exceed two inches in basal diameter, and three in height.

Scuta: these in young and moderately-sized specimens are striated, sometimes very faintly, but generally plainly, causing the lines of growth to be beaded; but often, in large and half-grown specimens, the lines of growth are extremely prominent, and being intersected by the radiating striæ, are converted into little teeth. As the striæ often run in pairs, the little teeth frequently stand in pairs, or broader teeth have a little notch on their summits, bearing a minute tuft of spines. In very old and large specimens, the prominent lines of growth are generally simply intersected by deep and narrow radiating striæ. In one case, a single zone of growth in one valve was quite smooth, whilst the zones above and below were denticulated. The valve varies in thickness, which I think influences the prominence of the lines of growth and the depth of the striæ. These striæ often affect the internal surface of the basal margin, making it bluntly toothed. The articular ridge is rather small, and moderately reflexed: the adductor ridge (as already stated,) varies remarkably; in most of the Panama specimens, it is extremely prominent, and extends down to near the basal margin; in other specimens it is but slightly prominent, especially in some of the fossil specimens from Virginia. The cavity for the lateral depressor, also, varies greatly; it is often bounded on the side towards the occludent margin by a very slight straight ridge, which occasionally folds a little over, making almost a tube; this, at first, I thought an excellent specific character, but far from this being the case, the cavity often becomes wide, quite open, and shallow.

Terga, very slightly beaked; the surface towards the carinal end of the valve, in some of the fossil specimens, is very slightly striated longitudinally. There is either a slight depression, or more commonly a deep longitudinal furrow, with the edges folded in and touching each other, extending down the valve to the spur, and causing the latter to vary in width relatively to its length. When the furrow is closed in, the spur is about one fourth of the entire width of the valve, and has its lower end obliquely rounded, and stands at about its own width from the basi-scutal angle: when there is only a slight depression and no furrow (as is always the case with young specimens), the spur is broader, equalling one third of the width of the valve, with its lower end almost truncated, and standing at about half its own width from the basi-scutal angle. But the absolute length of the spur, also, varies considerably; it is often very long, compared to the whole valve. The basal margin on the carinal side is sometimes slightly hollowed out; when the furrow is closed, this latter side slopes towards the spur. Internally, the articular ridge and crests for the tergal depressor muscle are moderately prominent.

Parietes, the longitudinal septa sometimes stand near each other, making the parietal pores small. The radii have oblique summits, but to a variable degree; their septa are unusually fine, and are denticulated on their lower sides; the interspaces are filled up solidly. The alæ have their summits very oblique, with their sutural edges nearly or quite smooth. In most of the fossil specimens, and slightly in some of the recent specimens, the surface of the sheath presents an unusual character, in a narrow, longitudinal, slightly raised border, running along the sutures, on the carinal side of each compartment.

Basis thin, porose; sometimes with an underlaying cancellated layer.

Mouth: labrum with six teeth: mandibles with the fourth and fifth teeth small, either sharp, or blunt: maxillæ with a straight edge, or with the inferior part slightly prominent. Cirri with the rami of the first pair unequal by four or five segments: the segments in the shorter ramus are extremely protuberant. The segments in the second cirrus only moderately protuberant: but all the specimens were in bad condition, and it appeared as if, in the Panama specimens, the segments of the second cirrus were more protuberant than in the Philippine Island specimens. In the posterior cirri there are from three to five pairs of spines on each segment: even amongst the Panama specimens some had three and some four pairs, and a white Panama specimen had five pairs of spines.

All the recent specimens which I have seen, were, with one exception, attached to various shells and crabs, and to each other. The Peruvian specimen was associated with B. flosculus. The tertiary specimens are often congregated together into great masses. Including the recent and fossil specimens, this species encircles the globe. During the miocene period it seems to have been the commonest existing sessile cirripede; now, it does not appear to be common, excepting, perhaps, at Panama: Mr. Cuming procured only one specimen from the Philippine archipelago.

19. BALANUS AMPHITRITE. Pl. 5, fig. 2 a-2 o.

LEPAS RADIATA. Wood’s General Conchology (1815), Pl. 7, fig. 7.

---- MINOR? Wood’s General Conchology (1815), Pl. 7, fig. 6.

---- BALANOIDES. Poli. Testacea utriusque Siciliæ (1795), Tab. 5.

BALANUS BALANOIDES. Risso. Hist. Nat. de l’Europe Merid., tom. iv, 1826.

Shell longitudinally striped with purple or pink; sometimes with the stripes confluent; sometimes wholly white. Scutum internally with a prominent broad adductor ridge.

Var. (1) communis: (2 e, 2 h, 2 l,) nearly white, with pale or dark violet-coloured longitudinal stripes: epidermis rarely persistent: shell either thin or thick: radii white or freckled with reddish mahogany colour, with their summits either oblique, sometimes in a high degree, or nearly parallel to the basis: basal point of spur of the tergum either square or bluntly pointed. Hab. Mediterranean, W. Indies, S. Africa, Philippine Archipelago, New South Wales.

Var. (2) venustus: (2 a,) white or pale pink, with narrow bright pink, or broad pinkish-purple stripes; orifice either much dentated or nearly entire. Tergum with the carinal half of the basal margin sometimes much hollowed out. Hab. W. and S. Africa, Ceylon.

Var. (3) pallidus: (2 c, 2 k,) white, with or without a yellowish persistent epidermis; sometimes with the edges of the compartments tinted purple: radii moderately oblique: tergum generally narrow, with the spur sharp, and the basal margin on its carinal side much hollowed out. Hab. W. Africa, Madagascar, Red Sea.

Var. (4) niveus: (2 f,) white, with longitudinal hyaline lines; epidermis not persistent. Hab. W. Indies, Florida, S. Africa, &c.

Var. (5) modestus: upper part of shell white, lower part uniform blueish-gray, opercular valves as in Var. (1). Hab. unknown.

Var. (6) Stutsburi: (2 d, 2 i, 2 m, 2 n, 2 o,) white, with or without pinkish-purple stripes, which are often confluent, rendering the lower part of the shell of a uniform purplish tint; epidermis persistent: radii very narrow: tergum narrow, spur sharp, varying in form and in exact position; carinal margin sometimes highly protuberant; basal margin on the carinal side of the spur generally, but not invariably, much hollowed out. Hab. West Africa.

Var. (7) obscurus: (Pl. 5, fig. 2 g,) with narrow, approximate, obscure and often almost confluent, slaty, or pale purplish-brown, or dark slate-coloured stripes. Hab. West Indies, Australia, and unknown.

Var. (8) variegatus: with narrow, approximate, dusky, claret-coloured stripes, transversely freckled with white; shell conical; walls very thin: scutum with the adductor ridge small. Hab. New Zealand.

Var. (9) (an. spec.?) cirratus: (fig. 2 b,) shell very pale purplish-brown, with faint, more or less plain longitudinal stripes, transversely freckled with white; walls thin: scuta with the lines of growth beaded: basis, in specimens growing in groups, irregularly cup formed: maxillæ with the inferior corner extremely prominent. Hab. Mouth of Indus, Australia, Philippine Archipelago.

Hab.—Warmer temperate and tropical seas; extremely common; Mediterranean, Smyrna, Sicily, Coast of Portugal; West Coast of Africa, River Gambia, West Indies, Demerara, Natal, Madagascar, Red Sea, Mouth of the Indus, Ceylon, Philippine Archipelago, East Indian Archipelago, Pacific Ocean, east coast of Australia, New Zealand; extremely common on ships’ bottoms; often attached to floating timber, canes, &c.; often associated with B. tintinnabulum; attached to pebbles and various shells.

With respect to the nomenclature of this extremely common species, which is widely distributed in all the warmer seas (excepting, as far as I have seen, on the west coast of America), there is some difficulty. I have no doubt that it is the Lepas radiata of Wood (1815), but Bruguière, in 1789, gave this same name to a Balanus which he had not seen, but which is figured in Chemnitz, Tab. 59, fig. 842. I should have thought that this also had been the present species, but Spengler, in describing (Skrifter af Naturhist. Selskabet i, B. 1790) this individual specimen, which he calls L. purpurea, states that it is 13 lines in basal diameter; now this is a size which is never acquired by B. amphitrite; and the description, habits, and size, would apply equally well to the species which I have called B. amaryllis; but when no notice is taken of such points of importance, as whether the walls are permeated by pores, whether the radii are smooth-edged, whether the scuta are striated, it is impossible to identify with any approach to certainty sessile Cirripedes; and the names given ought, in my opinion, to carry little weight with them. With respect to Lamarck’s Balanus radiatus (1818), the synonyms quoted exhibit some great and inextricable confusion. The B. radiatus, again, of Risso, is a fossil and apparently distinct species. There can be no doubt that the present species is the Lepas balanoides of Poli, (and of several authors who have followed him), and equally little doubt that the present species is not the true L. balanoides of Linnæus, which has a membranous basis, and which I have not seen from the Mediterranean. Under these circumstances I have concluded that less confusion would be caused by giving a new name to this species than by taking that of Wood, which ought not to have been used by him, considering Bruguière’s previous adoption of it.

Under the head of B. tintinnabulum I have alluded to the great variation of B. amphitrite, which consists not only in a vast diversity in the colouring and in the general aspect, but likewise in the degree of obliquity of the summits of the radii, in the form of the terga, and slightly in that of the scuta. In order to show that it has not been from indolence that I have put so many forms together, I may state that I had already named and fully described in detail eight of the following forms as species, when I became finally convinced that they were only varieties: it would require at least thirty figures, which I have not the power to give, fully to illustrate the transitional forms. As with B. tintinnabulum, the deception is wonderfully enhanced by whole groups of specimens from the same locality exactly resembling each other, and sometimes differing from other groups attached to the very same object. If a person were to get together only some fifty or sixty specimens from only half a dozen different localities, he would almost certainly come to the same conclusion, as I at first did, that several of the varieties are true species; but when he gets several hundred specimens from all quarters of the globe, he will find, to his trouble and vexation, that character after character fails and blends away by insensible degrees, and he will be led, as the more prudent course, to include, as I have done, and I hope rightly, all under one specific name. I have experienced more doubt regarding the last variety, cirratus, than on any other, on account of its peculiar colouring, and from the basis being often irregularly cup-formed. Under B. concavus I have remarked how closely some of its varieties approach to B. amphitrite, and it is to this last variety that they approach; almost the only difference being that the scuta in B. concavus are longitudinally striated. Yet some of the varieties of the two species are so distinct that it would be puerile to class them together. I will only add, that after studying such varying forms as B. tintinnabulum and amphitrite it is difficult to avoid, in utter despair, doubting whether there be such a thing as a distinct species, or at least more than half a dozen distinct species, in the whole genus Balanus.

As with B. tintinnabulum, I will first give a full description of the more common forms, alluding only to each less frequent variation, and then separately describe briefly the more marked varieties.

General Appearance.—Shape conical, either steep or considerably depressed; sometimes tubular; orifice either nearly entire or deeply toothed, not large, varying from rhomboidal to rounded-trigonal. Surface of shell smooth, never ribbed, generally naked, but occasionally the yellowish epidermis is persistent; in the same individual, I have seen all the lower part of the shell thus covered and the upper part naked, the line of separation being defined. The colour varies much, even sometimes considerably on the same individual; generally white or pale gray, with dull violet-coloured, longitudinal, moderately broad stripes; these stripes are sometimes equidistant, but more usually they are arranged so as to leave broad white spaces; the stripes fade away by endless variations, the edges of the compartments and the carinal end of the shell longest retaining any colour, until we have a uniformly white shell, generally covered with a yellowish epidermis; or the white is longitudinally marked with hyaline lines; this latter variety has a very peculiar aspect, and I did not doubt it was specifically distinct, until, in a number of specimens on a ship from the West Indies, I got the most perfect series, and another scarcely less perfect series from the Mediterranean, graduating into common coloured varieties. Rarely the dull violet or purple stripes become approximate and dark, so that the whole shell is tinted of a brownish slate-colour, occasionally freckled with white. Again, we have another set of very pretty varieties, with a white or very pale pink ground, with either narrow bright pink or broad pinkish-purple stripes. Again, I have seen numerous specimens of a variety, var. Stutsburi, from the west coast of Africa, in which the upper part of the shell is white, and the lower part shaded with pinkish or dark purple approximate stripes, which often become confluent; in one group, the whole shell being thus uniformly coloured, without any vestige of stripes. I have seen another group from an unknown locality, in which the lower part of the shell was uniformly blueish-gray. A variety from Australia has narrow approximate dark claret-coloured stripes, transversely freckled with white. Lastly, in the variety cirratus, the whole shell is very pale purplish-brown, with indistinct longitudinal brownish stripes, transversely freckled with white lines. I considered this as a distinct species, until quite lately finding forms which I could not possibly determine whether to class as B. cirratus or amphitrite.

The radii are generally snow-white, or freckled with a bright mahogany tint, or rarely clouded with purple, or in the pink varieties with pink. The scuta are dull purple or pink, generally with a white band along their tergal margin; often, however, they are white, with merely one or two purple fasciæ. The thickness or strength of the shells varies much; some specimens attached to a floating cane, from Natal and the Philippine Archipelago, were extremely strong; others, from the Mediterranean and Australia, and some tubular varieties from the West Indies, were very thin, translucent, and fragile. Size: large specimens generally attain a diameter of from half to three quarters of an inch in basal diameter; and I have seen one or two specimens an inch in diameter.

Scutum; sometimes the surface is very smooth, but generally the growth-ridges are moderately prominent; the latter are occasionally very finely beaded, and this seems always the case with var. cirratus. Internally, the articular ridge is prominent and reflexed: the adductor ridge is sharp, very prominent, and straight; it runs parallel to the occludent margin; close to its lower side there is often a depression (Pl. 5, fig. 2 i), sometimes bounded by a slight ridge, as if for the attachment of a muscle, but there certainly is no muscle here: rarely the adductor ridge is only slightly prominent: there is a small and shallow little pit of variable depth for the lateral depressor muscle.

Tergum (2 k-2 o); this valve is here far more variable than in any other species: in the commonest purple-striped forms (2 l), the valve is rather broad, the basal margin lies in nearly a straight line on the opposite sides of the spur, which is placed at rather less than its own width from the basi-scutal angle; the spur is rather short, and in width about one fourth of the entire valve; its lower end is either bluntly pointed or more commonly nearly square (2 k) and parallel to the basal margin: in young specimens it is generally sharper than in older ones. Externally, in the line of the spur, there is either a slight longitudinal depression, or more rarely a deep furrow. The carinal margin is more or less convex, and is formed by upturned lines of growth: the scutal margin is broadly inflected. Internally, the articular ridge in the upper part is very prominent: the crests for the tergal depressor muscle are moderately prominent, but very variable. Sometimes the carinal portion of the basal margin is slightly hollowed out. In var. Stutsburi (2 m, 2 n, 2 o), and in some white varieties, which differ most in the shape of the tergum from the commoner varieties, the whole valve is narrower, the spur is much sharper and narrower, the carinal half of the basal margin is much hollowed out and slopes down towards the spur, with the crests for the depressor muscles depending beneath the basal margin, and with the carinal margin sometimes extremely convex or protuberant. But the shape and position of the spur, and the outline of the carinal half of the basal margin vary much in nearly all the varieties.

Compartments.—The upper parts of the parietal pores are either filled up solidly with, generally coloured, shell, or they are crossed by thin transverse calcerous septa: the longitudinal parietal septa occasionally bifurcate at their bases close to the outer lamina, making an irregular outer row of minute pores. The Radii have their septa rather fine, and finely denticulated on both sides, but sometimes only on the lower side; the thickness of the septa varies a little; the interspaces are filled up solidly; the summits of the radii are jagged and oblique, and usually form an angle of about 45° with the basis, not being added to above the level of the opercular membrane; but not rarely they reach up much higher, and are very nearly parallel to the basis, extending from tip to tip of the compartments. Again, in some ordinary varieties, and always in var. Stutsburi, the summits of the radii are extremely oblique, the radii themselves forming a mere border to the compartments to which they belong. In no other species have I seen so great an amount of variation in the form of the summits of the radii. The alæ, in like manner, have their summits either very oblique, not being added to above the opercular membrane, or they are only slightly oblique; it often happens that in those specimens in which the summits of the radii are nearly parallel to the basis, the alæ are very oblique, and the converse: in other individuals, both radii and alæ have equally oblique summits. The sutural edges of the alæ vary in thickness, being either very thin and obscurely crenated, or moderately thick and ribbed. The basis is porose; but I have never seen an underlying cancellated layer of shell, as is so common in several species.

Mouth: labrum, with from four to eight, generally with six, little teeth: mandibles with three teeth, and two minute lower teeth, or mere knobs: maxillæ with the edge straight, or with the inferior part forming a slightly step-formed projection. Cirri: the rami of the first pair are unequal by three or four segments, but in some specimens by five or six segments, with the front surfaces of the segments in the shorter ramus extremely protuberant. The second pair of cirri are short, with the front surfaces of the segments moderately protuberant: the third pair have a tuft of bristles at their bases on the thorax. The segments in the sixth pair have from four to six pairs of spines on the segments; equal-sized specimens seem to vary in this latter respect. There is a small sharp projection on the dorsal base of the penis.

Varieties.

With respect to var. 1, communis, I have nothing further to remark, except that I have seen specimens identically similar from the Mediterranean, Natal, the Philippine Archipelago, and Sydney; at the latter place it is said to be rare, but in most places it is the commonest variety, and is often attached to ships’ bottoms. Of var. 2, venustus, I have seen specimens from the west coast of Africa, Natal, and Ceylon, in groups by themselves, and associated with var. communis; it is much less common than var. 1. The third variety, pallidus, is not uncommon; I have seen many specimens from the bottoms of ships, from the West Indies, and the west coast of Africa. Of the var. 4, niveus, I have seen the most perfect graduated series passing into var. 1, both from the West Indies, Florida, and the Mediterranean: I have seen other specimens from the Red Sea and Madagascar. Of the var. 5, modestus, I have seen only one group from an unknown locality; it is only remarkable from its uniform colouring. The var. 6, Stutsburi, is more remarkable than the foregoing; until quite lately I did not doubt that it was specifically distinct; but as I have seen every character graduate into other varieties, I am now convinced that it is not a true species: all the specimens which I have seen have come on shells, or on ships’ bottoms, from West Africa. Of var. 7, obscurus, I have seen three or four groups of specimens from unknown quarters, both on pebbles, shells, and on cork (probably from the Atlantic ocean); and likewise some specimens taken from the bottom of Her Majesty’s ship “Fly,” on the east coast of Australia; these latter are intermediate in character with the next var. variegatus; from the Australian seas, which I at first ranked as an undoubted species, but I have subsequently failed in discovering any sufficient diagnostic character. Lastly, of var. cirratus, I have seen several groups of specimens from India and the Philippine Archipelago, and a group intermediate in character between this and the first and third varieties, from Australia; I retained this variety owing to its peculiar freckled, pale brown colouring and beaded scuta (of which, however, I have seen decided traces in the common variety), as a distinct species, after I had given up all the foregoing forms. I entertain some doubts whether I have now acted right; but when I found some specimens which, I found it impossible to decide, whether to rank as amphitrite or cirratus, I determined to take the more prudent course, and sink the latter as a species. This variety, also, seems to connect B. amphitrite and concavus very closely.

20. BALANUS PŒCILUS. Pl. 5, fig. 3 a, 3 b.

Shell dull red, freckled with white. Scutum internally without an adductor ridge; tergum with the spur, sharply truncated, almost one third of width of valve.

Hab.—West coast of South America, Mus. Cuming; attached to an Avicula.

The appearance of the fragile shell, in the one group of specimens which I have seen, leads me to suspect that they may have grown under unfavorable circumstances. This species differs considerably in general aspect, but not much in essential characters, from B. amphitrite; the absence, however, of an adductor ridge to the scutum, and the sharply truncated spur of the tergum, are sufficient to distinguish them. In the opercular valves this species comes near to B. vinaceus, also from the west coast of South America; but the striated scuta of that species, the cancellated inner lamina of the parietes, the general colouring, and square porose radii, are amply diagnostic characters.

General Appearance.—Shell fragile, tubulo-conical, orifice large, passing from diamond-shaped into oval. Colour fine dark rose, freckled with transverse, sharply pointed, fine zig-zag white lines: the pink is also so arranged as to obscurely give to the walls a longitudinally striped appearance: radii generally rather whiter than the walls, and similarly freckled: terga similarly freckled: scuta dull red, with a white band along the scutal margin. Basal diameter of largest specimen half an inch.

Scutum, externally smooth: internally, articular ridge moderately developed, slightly reflexed: there is no adductor ridge: there is a distinct pit for the lateral depressor muscle. Tergum, with the scutal margin unusually prominent, toothed: longitudinal furrow shallow, the edges apparently having no tendency to fold in: spur short, barely one third of width of valve, with the lower end sharply truncated, parallel to the basal margin: articular ridge and crests for the depressores moderately prominent.

Compartments.—Walls very fragile, with the outer lamina not thicker than the inner lamina. Radii fragile, broad, with their summits moderately oblique; their sutural edges have the septa plainly denticulated on both sides, with the interspaces filled up solidly nearly to the tips of the septa. Alæ, with their summits more oblique than those of the radii; their sutural edges smooth. Basis with an underlying cancellated layer. Mouth: labrum with three unusually large teeth on each side of the notch: mandibles with the fourth tooth tolerably well developed, the fifth being confluent with the inferior angle. Maxillæ simple. Cirri,—first pair with one ramus longer by about four segments than the other ramus, which has considerably protuberant segments: second pair with segments only moderately protuberant: sixth pair with segments much elongated, but bearing only four pairs of spines.

21. BALANUS EBURNEUS. Pl. 5, fig. 4 a-4 d.

BALANUS EBURNEUS. Aug. Gould (!). Report on the Invertebrata of Massachussetts, 1841, fig. 6.

Shell yellowish white. Scutum striated longitudinally: tergum with the spur truncated, the basi-carinal margin generally much hollowed out, and the carinal margin protuberant in the upper part.

Hab.—United States, from about lat. 42° to Charlestown; West Indies; Honduras; Venezuela; attached to shells and floating wood. Attached to ships’ bottoms from Trinidad and Jamaica, associated with B. tintinnabulum, amphitrite, and improvisus. Brackish water, Salem, Massachussetts, according to Mr. Stimpson. Mus. Aug. Gould, Agassiz, Stutchbury, Cuming, W. Dunker, &c.; very common.

General Appearance.—Shell conical, or almost tubular; white, with the surface very smooth, covered by thin yellowish epidermis, but with the radii naked. Orifice large, passing from rhomboidal into pentagonal, moderately toothed. Average full size, about one inch in basal diameter; I have seen a specimen 1.3 in basal diameter, and the same in height.

Scutum, plainly striated longitudinally: the teeth on the occludent margin small. Internally, the upper surface is roughened: the articular ridge is prominent, and either slightly or not at all reflexed: the pit for the adductor muscle is distinct; the adductor ridge is prominent in a variable degree, and is almost confluent with the articular ridge. In one specimen from Beverly Bay, U. S., the scuta were extraordinarily disintegrated, and I could perceive no trace of the external radiating striæ. Tergum, with the basal margin on the carinal side of the spur sometimes deeply (Pl. 5, fig. 4 b), and sometimes only slightly (fig. 4 d), and rarely hardly at all, hollowed out: when much hollowed out the valve may almost be said to be two-pronged, with the carinal prong narrower than the spur. There is no distinct longitudinal furrow, but the whole scutal margin projects above the general surface of the valve. In the carinal margin, in the upper part, there is a remarkable convexity or protuberance in the same plane with the valve, from which it is separated by a very slight and narrow ridge. The spur is about one fourth of the width of the valve, with its lower end abruptly truncated. Internally, the upper surface is much roughened with finely crenated ridges: the distinct crests for the depressores cover the whole of the so-called carinal prong.

Compartments; the radii and alæ have their summits oblique, sometimes a little rounded, but not smooth. The septa on the sutural edges of the radii are remarkably fine, and closely approximate; the denticuli are excessively minute. The sutural edges of the alæ are most delicately crenated; the alæ are largely added to during the diametric growth of the shell, and above the level of the opercular membrane. The parietal pores are square and rather large: they are crossed by transverse septa almost close down to the basis: the longitudinal septa have tolerably large denticuli at their bases. The pores in the basis are crossed by numerous transverse septa. When specimens grow in a group, the basis is sometimes irregularly cup-formed.

Mouth: labrum serrated with small teeth, decreasing in size downwards, on each side of the central notch. Mandibles with the third tooth rather thick and blunt, and with the fourth and fifth knob-like. Maxillæ, with the inferior part projecting much beyond the rest of the edge, and bearing two long single spines: between these two spines and the large upper pair, there are, in a full-sized specimen, about seven pairs of moderately long spines, feathered on their sides. Outer maxillæ thickly clothed with very fine spines, and remarkably prominent.

Cirri: first cirrus, with one ramus having twenty-six segments, and longer by ten segments than the shorter ramus, which has sixteen segments: the shorter ramus, and both ramii of the second pair, have their segments remarkably protuberant in front; the protuberance, in the upper segments, equalling in length the supporting part of each segment: rami of the second cirrus unequal in length by five segments. Third cirrus with the segments only slightly protuberant; rami considerably longer than those of the second cirrus: at the dorsal base of the pedicel of this third cirrus there is no tuft of fine hairs, as is common in many other species. Sixth pair, with the upper segments elongated, bearing from six to seven pairs of spines; dorsal spines short, thin, and few.

Affinities: in external appearance of the shell, this species can hardly be distinguished from some of the white varieties of B. amphitrite; and there is a considerable resemblance, in some of the varieties, in the opercular valves; but the longitudinally striated scuta of B. eburneus suffice to distinguish these certainly very distinct species. Equally, or even more like externally, is this species to the B. Hameri, so that I have received from an eminent naturalist in the United States both species mingled in the same lot, all bearing the same name of B. eburneus; but when the internal structure of the shell is examined, the species are at once seen to be far removed from each other. Still more close is the affinity of this species to B. improvisus, both in internal and external characters: it agrees with this species in the singular habit of being able to live in brackish water: these two species are the only ones which have the labrum serrated with teeth, graduated in size, on each side of the central notch. In the case of young specimens of the var. assimilis of B. improvisus, an inhabitant of the same seas with B. eburneus, the diagnosis is most difficult without long practice; for in the young of eburneus, the compartments are only partially covered by yellow epidermis, and have a striped appearance, the radii are sometimes very oblique, the scuta externally have not acquired their longitudinal striæ, and internally the adductor ridge lies not so close to the articular ridge as it does subsequently; hence I for some time mistook the var. assimilis of B. improvisus for the young of B. eburneus. But I found in the latter, that the rami of the first pair of cirri, are always, even in the earliest youth, more unequal in length, and that each segment of the posterior cirri bears a greater number of pairs of spines, there being, even in very minute specimens, seven pairs. Moreover, after having examined scores of specimens, I found I could almost always distinguish the two species by the smoothness and curvature of the summits of the radii of B. improvisus; I entertain no doubt whatever about the distinctness of the two species; indeed, when both are mature, besides the greater size, striated scuta, &c. of B. eburneus, their general aspect is very different.

22. BALANUS IMPROVISUS. Pl. 6, fig. 1 a-1 c.

Shell white: radii narrow, with their upper margins smooth, slightly arched, very oblique. Tergum with a longitudinal furrow; spur with the end rounded.

Var. assimilis, with longitudinal white hyaline lines.

Hab.—England, Scotland, Belgium (?), Nova Scotia, United States, West Indies, Rio Plata, Southern Patagonia, Guayaquil, West Colombia; attached to wood, shells, rocks, ships’ bottoms, from low tidal level to twenty fathoms depth.

General Appearance.—Shell conical, with a rather large diamond-shaped orifice, moderately or but little toothed; very smooth; walls never folded longitudinally; white, with an extremely thin pale-yellow persistent epidermis. The radii are very narrow, with their summits very oblique, rounded, and smooth; the epidermis is generally more persistent on the radii than on other parts, and this is exactly the reverse of what is common with B. eburneus. The specimens from nearly fresh-water in the R. Plata (hereafter to be mentioned), are brownish, and have undergone a remarkable degree of corrosion, the outer lamina of the walls having been entirely removed to near the base; hence the external aspect of these specimens is wholly different from ordinary individuals. The var. assimilis has also a very different appearance, owing to the dead white of the walls being relieved by narrow approximate longitudinal hyaline lines, corresponding with and caused by the longitudinal parietal septa being externally visible through the outer lamina of the parietes; the epidermis on the radii is also of a rather brighter yellow. The largest specimens which I have seen are those from the Plata, and those attached to a ship from the West Indies, and they had a basal diameter of .6 of an inch: from .4 to .5 of an inch is the more usual full average size.

Scuta, with the lines of growth but little prominent: articular ridge prominent, but little reflexed: adductor ridge straight and very prominent, varying a little in its distance from the articular ridge; there is scarcely any depression for the lateral depressor muscle; the upper internal surface of the valve is roughened with ridges. Terga, with a moderately deep longitudinal furrow; spur short, rather narrow, with the end rounded, placed at less than its own width from the basi-scutal angle; in the Rio Plata specimens the spur is close to this angle: the basal margin is generally straight on opposite sides of the spur, but sometimes on the carinal side it is a little hollowed out. The lines of growth are upturned along the carinal margin, which consequently is a little protuberant, but to a varying degree. The crests for the depressores are extremely distinct and prominent. In the varieties having the basi-carinal margin hollowed out, and the carinal margin protuberant, there is a marked resemblance to the peculiar tergum of B. eburneus.

Walls: the parietal pores are tolerably large, and are crossed by numerous transverse septa: the longitudinal septa are very finely denticulated at their bases, but occasionally almost smooth. The radii are, as stated, extremely narrow, and very remarkable from their smooth rounded edges; their septa are barely denticulated. The alæ are remarkably protuberant; they have their summits much less oblique than those of the radii, and sometimes they are almost parallel to the basis: their sutural edges are coarsely crenated. Basis, flat, thin, permeated by pores, but the pores do not generally run to the very centre; they are, as usual, crossed by transverse septa.

Mouth: the labrum is the most remarkable part; on each side of the central notch there are generally two teeth; and on the two sides of the notch itself nine or eleven smaller teeth, decreasing regularly in size downwards till they become so minute as to be hardly visible even under the compound microscope; thus, in the two specimens closely examined, there were altogether twenty-two and twenty-six teeth on the labrum. Mandibles with the two inferior teeth reduced to mere knobs: maxillæ with the lower part of the edge bearing two large spines, and generally, but not always, forming a step-formed projection. Cirri: the ramii of the first pair are but slightly unequal; in one specimen examined there were fifteen segments in one ramus and twelve in the other: segments very protuberant in front. Second cirrus with the segments only slightly protuberant; segments thirteen. Third cirrus longer than the second pair, with the rami rather unequal in length: there is a tuft of long spines on the basal segment of the pedicel of this cirrus. Fourth cirrus twenty-two segments. Sixth cirrus, in the same individual, thirty-four segments: on each of these segments there are five or six pairs of spines. I may specify that the longer ramus of the first cirrus of a large Rio Plata specimen had twenty-four segments.

Varieties, affinities.—When I first met with the var. assimilis, misguided by its general aspect, I did not doubt that it was specifically distinct; I was strengthened in this view by the absolute identity of several hundred specimens attached to two vessels from Jamaica and Trinidad, in the West Indies, with one specimen from Charlestown, in the United States, sent me by Prof. Agassiz, and with several in three lots from the western tropical shores of South America: yet on close examination I can point out no one distinguishing character, either in the shell or animal’s body, excepting the longitudinal hyaline lines on parietes, due to the septa being externally visible. The presence of similar lines is variable in white vars. of B. amaryllis and amphitrite, and they are seen in very young specimens of B. eburneus: hence it is impossible to consider so trifling a character as specific; moreover, lately I have seen a British specimen with hyaline lines, and some few other specimens in an intermediate condition. Under the head of B. eburneus, I have stated that although that species and B. improvisus, which in the West Indies are associated together, are most readily discriminated when old, yet when young, they so closely resemble each other that the eye requires much practice to separate them. On account of this species and B. crenatus being sometimes associated together on the shores of England, I have pointed out under B. crenatus, the relative diagnostic characters of the two. The chief affinity of B. improvisus is certainly towards B. eburneus; but in the narrow, oblique, rounded, and smooth-edged radii, there is a relationship shown to the species in the last section of the genus, such as B. amaryllis, and more especially to the fossil B. dolosus: so close is the resemblance in the external appearance of the shell, and in the structure of the opercular valves, to the latter species, that I for some time did not discover their distinctness. Balanus improvisus has hitherto been overlooked by naturalists, and has probably been confounded with B. crenatus or balanoides.

Range and habits.—This species, as far as my experience goes, is commoner on the shores of Kent than on other parts of England: the first specimens which I met with, I owed to the kindness of Mr. Metcalf, they were attached to wooden stakes from Herne Bay, together with a single specimen of B. crenatus: I have seen other specimens from near Woolwich, from the Kentish oyster-beds, from Sandwich, and from Ramsgate. The only other British specimens which I have seen are from the River Itchen, in Hampshire, and from Loch Shieldaig, in Ross-shire (Mus. Jeffreys), from a depth of twenty fathoms. This species is often attached to wood. At Ramsgate, the specimens were attached to a small coasting vessel, and they must have been immersed five or six feet; they were associated with B. crenatus, and with a few of B. balanoides. In the Brit. Mus. there are specimens collected by Mr. Redman, from Nova Scotia, in North America. When her Majesty’s ship Beagle was beached at Santa Cruz, in Southern Patagonia, numerous specimens were found adhering to her copper bottom, some so small as to show that the species breeds in those latitudes. Near Monte Video, in the estuary of La Plata, I found many large, but much corroded specimens, adhering to some rocks in a small running stream of perfectly fresh water. The rise of the tide is here small, but at high water the specimens apparently were for a short time covered by the waters of the estuary, here itself only brackish, and occasionally almost fresh. I took home some specimens, and placing them in perfectly fresh water they continued for many hours expanding and retracting their cirri with perfect regularity and vigour. Here then we have a Balanus capable of living in fresh water, and likewise in the saltest seas: even brackish water is a deadly poison to several, probably to most, species of the genus; but this, as we have seen, is not the case with the allied B. eburneus. The water, I may add, at Woolwich, on the Thames, whence I have received B. improvisus, must at times be very brackish. I have already incidentally mentioned that the var. assimilis was attached in great numbers, associated with B. eburneus, tintinnabulum, and amphitrite, on vessels from the West Indies: one specimen sent me by Prof. Agassiz, from Charlestown, was attached to a specimen of B. eburneus; and, lastly, I have seen three sets of the same identical variety attached to shells from Guayaquil (in Mus. Brit. and Cuming), and from West Colombia. Here, then, we have the same species with an enormous range, from Nova Scotia and Great Britain to South Patagonia; and, which is the case with scarcely a single mollusc, it lives both on the eastern and western tropical shores of the South American continent.

23. BALANUS NUBILUS. Pl. 6, fig. 2 a-2 c.

Shell white, rugged: basis in parts imperfectly porose. Scutum with the articular ridge minute; adductor ridge prominent, forming a deep pit for the lateral depressor muscle: tergum with an internal patch of purple; apex produced, purple.

Hab.—California, Mus. Brit. and Aug. Gould; associated with B. glandula, and attached to wood.

I have seen two specimens of this species, brought by Lady K. Douglas from California; and two from Monterey, sent me by Dr. Aug. Gould. This is a very distinct species, coming nearer to B. porcatus than to any other species: it is also allied to B. cariosus. In the basis being in parts solid or not permeated by pores, it has claims to be placed in the next section, in which I at one time included it.

General Appearance.—Shell conical, rugged, sometimes furnished with sharp longitudinal ribs; dirty white. Orifice not large, oval, toothed. Radii rather narrow, with their summits oblique, much jagged. Basal diameter of largest specimen 2.1; height only 1.3 of an inch.

Scuta, broad, with the lines of growth prominent; internally, articular ridge very little prominent, sometimes hardly developed, but thick, ending downwards in a small free point. Adductor ridge prominent, blunt, produced straight downwards, making a deep longitudinal cavity for the lateral depressor muscle; in some specimens this cavity is almost arched over, so as to tend to be tubular, with a short ridge in the middle (Pl. 6, fig. 2 a): in other specimens there is no trace of this tubular structure. Terga, with the apex beaked, beak triangular, dull purple; the longitudinal furrow is so shallow as hardly to exist. The basal margin slopes down on both sides, with a nearly equable curvature towards the spur; hence the spur is broad in its upper part, and narrow at its obliquely truncated lower end. Internally, there is an elongated dark purple patch: the shallow articular furrow is of quite remarkable breadth; the articular ridge is medial, and the inflected scutal margin is not wide. The internal surface of the spur is formed into a ridge, which runs a little way up the valve, and is sometimes partially separated from the spur itself (fig. 2 c), making the basal extremity toothed or double. The crests for the depressores are pretty well developed.

Walls, moderately strong: inner lamina slightly ribbed: the denticuli on the bases of the parietal longitudinal septa are sharp: I could not see any transverse septa in the parietal tubes. The radii are rather narrow; their summits are remarkably jagged and very oblique; the septa are plainly denticulated on both sides, but chiefly on the lower side; each septum itself, towards the inner lamina of the radius, branches and divides: the interspaces are filled up nearly solidly. The alæ have apparently their summits less oblique than those of the radii: their sutural edges are finely crenated. The lower edge of the sheath is hollow underneath. The basis is flat; it is rather thin, and imperfectly porose; in parts it is not at all porose, in others it is traversed only by very minute pores: there is nevertheless, in some parts, even where the upper layer is not porose, an underlying, cancellated layer.

Animal’s body unknown.

24. BALANUS CORRUGATUS. Pl. 6, fig. 3 a, 3 b.

Shell white, longitudinally folded; radii narrow. Scutum internally without an adductor ridge.

Fossil, Sub-Appennine formations; Colle in Tuscany; Mus. Greenough.

I have seen only two specimens of this species attached to rock, collected by Mr. Greenough, at Colle, and kindly given by him to me. The species comes near to the living B. crenatus, also found fossil in deposits of this same age; it differs, however, distinctly from that species, in having its basis permeated by pores, and, in a less degree, in the sutural edges of the radii being more plainly crenated: the opercular valves of the two species closely resemble each other. This may be the B. stellaris of Bronn, but it is futile attempting to identify the species of this genus merely by external characters, even when aided, as in this case, by an excellent drawing of the shell.

General Appearance.—Shell conical, with broad rounded longitudinal folds; orifice of moderate size, oval; radii narrow, with their upper margins oblique; but the summits of both specimens had been much broken. Colour, as it appears, originally white. Basal diameter of largest specimen 3/4 of an inch.

Scuta, with the upper portion much reflexed; the articular ridge is very prominent, and the articular furrow of great width; when the valve is viewed from the outside the articular ridge is very conspicuous: there is no adductor ridge. Terga, with the longitudinal furrow very slight; the spur is from one third to one fourth of the width of the valve, and its basal end is blunt and almost truncated; it stands about half its own width from the basi-scutal angle. Internally, the articular ridge is very prominent, and the articular furrow narrow and deep, extending down the valve in the line of the spur.

Parietes: the parietal tubes are remarkably large, and I think this can hardly be an individual peculiarity: the tubes are crossed by many transverse septa, close down to the basis. The radii are narrow, and have jagged, oblique summits: their sutural edges have very distinct septa, barely denticulated, with the interspaces filled up solidly. The alæ have oblique summits; I was unable to make out the structure of their sutural edges. The Basis is very distinctly permeated by pores, which are crossed by transverse septa.

The shell and opercular valves of B. corrugatus so closely resemble the same parts in B. crenatus, that I should not be much surprised at seeing the two species graduating into each other, if a larger series of specimens, from beds intermediate in age between the Sub-Appennine formations and the present time, were obtained. If indeed the basis of B. crenatus were permeated by pores, the two species could hardly be discriminated.