Part 29

_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.

_Section_ D.

_Parietes permeated by pores. Basis and Radii not permeated by pores._

25. BALANUS PORCATUS. Pl. 6, fig. 4 _a_-4 _e_.

BALANUS PORCATUS. _Emanuel da Costa._ Hist. Nat. Test. Brit., p. 249 (1778).

LEPAS BALANUS. _Linn._ Syst. Naturæ (1767).

---- ---- _Born._ Testacea Mus. Cæs. Desc., Tab. 1, fig. 4, (1780).

---- ---- _Chemnitz._ Syst. Conch., 8 Band., Tab. 97, fig. 820, (1785).

BALANUS ARCTICA PATELLIFORMIS. _Ellis._ Philosoph. Transact., vol. 50, Tab. 34, fig. 18 (1758).

---- SULCATUS. _Bruguière._ Encyclop. Method., Tab. 164, fig. 1 (1789).

LEPAS COSTATA and BALANUS. _Donovan._ British Shells, 1802-1804, Tab. 30, fig. 1, 2.

LEPAS SCOTICA. _W. Wood._ General Conchology, Pl. 6, fig. 3, sed non _Lepas balanus_, Pl. 7, fig. 3, (1815).

BALANUS ANGULOSUS. _Lamarck_ (1818), in _Chenu_, Illust. Conch., Tab. 11, fig. 11.

---- TESSELATUS. _Sowerby_ (!). Mineral Conchology, Tab. 84 (1818).

---- SCOTICUS. _Brown._ Illust. Conch. Great Britain, Pl. 7, fig. 2, sed non, Pl. 6, fig. 9 et 10 (1827); 2d edit., Pl. 53, fig. 1-3, 22, 23 et Pl. 54, fig. 1-3.

---- GENICULATUS. _Conrad._ Journal Acad. Philadelphia, vol. 6, part 2, p. 265 (1830), Tab. 11, fig. 16.

---- ---- _Aug. Gould_ (!). Report on the Invertebrata of Massachussetts, fig. 9 (1841).

_Shell white, generally sharply ribbed longitudinally: radii with their summits almost parallel to the basis. Scutum longitudinally striated: tergum with the apex produced and purple._

_Var._ (_a_): _Walls without longitudinal ribs_. Mus. Brit., Cuming, Stutchbury, Jeffreys.

_Hab._--South shores of England, Ireland, Scotland, Shetland Islands, Iceland, Davis's Straits, 66° 30′ N.; Lancaster Sound, 74° 48′ N. (Mr. Sutherland). Maine and Massachussetts, United States. China (?). In deep water, common on shells, crustacea, and rocks, sometimes imbedded in sponges.

_Fossil_ in the glacial deposits of Scotland, Uddevalla, and Canada; in the mammaliferous and Red Crag of England; Mus. Lyell, Sowerby, S. Wood, &c.

_General Appearance._--Shell conical, somewhat convex; white, sometimes tinted yellowish, from the thin investing membrane; the produced tips of the terga are purple: the parietes of each compartment have from two to four strong, prominent, sharp, straight longitudinal ribs; these are sometimes irregular, and rarely, as will presently be described, they are absent. The radii are smooth and of considerable breadth; their summits are nearly parallel to the basis or only slightly oblique: hence the orifice is entire; it is rather small and ovate, being broad at the rostral end, and very sharp and narrow at the carinal end.

_Dimensions._--The largest specimens which I have seen from Great Britain or Ireland, have been 1.3 of an inch in basal diameter: in Mr. Cuming's collection, however, there was one much depressed specimen from the Shetland Islands, 2.1 in basal diameter: a regularly conical specimen from the coast of Massachussetts attained a nearly equal diameter; out of the glacial deposits in the Isle of Bute, Scotland, several specimens had this same diameter, namely, two inches, and were even more steeply conical, being 1.85 in height; some glacial specimens from Uddevalla and Canada, in Sir C. Lyell's collection, were 1.7 in basal diameter. Hence, it appears, as we shall presently see is likewise the case with _B. crenatus_ and _Hameri_, that northern specimens, and those from the United States and from the glacial deposits, often exceed in dimensions those from Great Britain or Ireland.

_Scutum_: the lines or ridges of growth are broad and prominent; they are divided into square beads by fine striæ, radiating from the apex: and hence the valve is longitudinally striated. Internally, the articular ridge is extremely little prominent; the adductor ridge, or what must be called such, runs straight down under the articular ridge, making a deep longitudinal pit for the lateral depressor muscle. _Tergum_: the apex is a little produced, and coloured purple, as well as the upper internal surface of the valve; there is no longitudinal furrow, only a very slight depression: the spur is placed close to the basi-scutal angle; it is rather long, and measured across the upper part, is half as wide as the valve: its lower end is truncated and rounded; the basal margin slopes towards it. Internally, a very small portion of the scutal margin is inflected: the articular furrow is shallow and broad: the crests for the depressores are feeble. In young specimens the spur is bluntly pointed.

The _Parietes_ (4 _e_) have large square parietal tubes: in the upper part these are filled up solidly without transverse septa: the longitudinal septa are finely denticulated at their bases, and the denticuli extend unusually close to the outer lamina. In very young specimens the inner lamina of the parietes is ribbed, in lines corresponding with the longitudinal septa, as is the case with most species of the genus; but in medium and large-sized specimens, there are between the ribs, thus produced, from one to four smaller ribs, which do not correspond with any longitudinal septa; they are finely denticulated at their bases, and may be considered as the representatives of longitudinal septa which have not been developed and reached the outer lamina. I have seen no other instance of this structure, namely, the presence of a greater number of ribs, on the inner lamina of the walls, than there are longitudinal septa. The _radii_ have their summits generally parallel to the surface of attachment, as is usual in the first section of the genus, but sometimes they are slightly oblique: the septa sometimes rudely branch a little, but they exhibit scarcely a trace of denticuli: the interspaces are filled up quite solidly. The _alæ_ have their summits very oblique; their sutural edges are finely crenated.

_Basis_, rather thin, translucent, not permeated by pores; obscurely furrowed in lines radiating from the centre: the circumference is marked in a peculiar manner by the longitudinal septa, and by the tips of those intermediate, denticulated ribs, which occur on the inner lamina of the parietes.

_Mouth_: labrum with six teeth: mandibles with the fourth and fifth teeth small and rudimentary: maxillæ, with a small notch under the upper pair of spines; in the lower part there is a single large spine. _Cirri_, dark brownish purple, making a singular contrast with the white operculum and shell; first pair, with one ramus, having twenty-six segments, and about twice as long as the shorter ramus, having twelve or thirteen segments, with their front surfaces protuberant. In the second pair the segments are but little protuberant: third pair about one third longer than the second pair: sixth pair, elongated, having in the same individual forty-six segments; these segments have shield-shaped fronts, bearing five pairs of spines, with some minute intermediate bristles. There is the usual point at the dorsal base of the penis.

_Range: Geological History._--This species is common on the shores of Scotland and Ireland; the most southern point of Europe whence I have happened to see a specimen is Tenby, in South Wales: but I have no doubt it is found further south; and Mr. Jeffreys, who knows this species well, has found it common on the extreme southern shores of England. In the United States, it is found on the shores of Maine and Massachussetts: northward, I have seen specimens from Iceland, from Davis's Straits, and from Lancaster Sound, in lat. 74° 48′ north; these latter I owe to Sir J. Richardson. It is an inhabitant of deep water; in Mr. Thompson's collection there are several specimens from the Bay of Belfast, marked twenty-five fathoms, and one group said to have come from "about fifty fathoms, on the coast of Antrim:" one specimen from Cape St. Anne, Massachussetts, is marked as having come from only five fathoms. This species is commonly associated, on both sides of the Atlantic, with _B. crenatus_, and sometimes with _B. Hameri_ and _Verruca Strömia_: mollusca, such as pectens, modioli, and oysters, offer the most usual surfaces of attachment: I have, however, seen many specimens on crustaceans, on rocks, and even on the roots of the larger sea-weeds. This species is very common in the glacial deposits of Uddevalla, of Skien in Norway, and of Canada, and is associated with the same species as in the living state: I have seen, also, specimens from the same formation in the Island of Bute, Scotland. I have seen numerous specimens from the mammaliferous crag, and a few from the Red Crag of England. I owe to the kindness of Mr. J. de C. Sowerby an inspection of the original specimens of the _B. tesselatus_ of the Mineral Conchology, which is certainly the present species.

_Affinities._--This species is very distinct from every other; it comes nearest, as shown in all the characters derived from its opercular valves, to _B. nubilus_, and in this latter species we have seen the basis plainly tending to lose its pores and thus become solid. _B. porcatus_ is perhaps allied in some degree to _B. trigonus_, and slightly to _B. crenatus_. The rather broad radii, with their summits hardly oblique, give this species a very different aspect from those species of the genus amongst which it must be placed.

_Varieties._--A conical specimen, sent to me from the coast of Massachussetts, is remarkable from the radii not having been at all developed, being represented by mere fissures. I have seen a few specimens of _var._ (_a_), (one collected by Sir E. Parry in the arctic seas) which had a remarkably different aspect from the common forms, but which, after a careful examination of the opercular valves and of the animal's body, I feel convinced are not specifically distinct: they are characterised by the walls being smooth and absolutely destitute of the external longitudinal ribs; by the shell being more cylindrical, with broader radii, and with the orifice larger and more rhomboidal; the walls and radii are much thinner, and the internal lamina is less plainly ribbed: the beak of the tergum is not purple. As most of these specimens had grown in a group crowded together, the difference of shape, and perhaps the thinness of the walls, is thus explained. In a specimen from Davis's Straits, in Mr. A. Hancock's collection, most of the above characters are in an intermediate condition; there are only a few external longitudinal ribs on the parietes; and the terga have not purple apices. In Mr. Cuming's collection there are some fine, brilliantly white specimens (_without opercula_) from the coast of China; these have thin walls and radii, and the walls are not longitudinally ribbed, but they are not smooth: the orifice is not large, nor the shape of the whole shell cylindrical. It is just possible that these latter specimens may be a distinct and representative species, but I do not think so.

26. BALANUS PATELLARIS. Pl. 6, fig. 5 _a_-5 _c_.

LEPAS PATELLARIS, (_Gmelin_). _Spengler._ Schriften der Berlin. Gesellschaft, &c. b. i (1780), Tab. 5; Chemnitz, Neues Syst. Couch., Tab. 98, fig. 839.

_Shell depressed; brown, generally with obscure longitudinal violet stripes: radii (in full-grown specimens) with their summits rounded and surfaces finely ribbed parallel to the basis: basis sometimes permeated by imperfect pores. Scutum internally with an adductor ridge._

_Hab._--Bengal, on wood, Mus. Brit.; on a shell, Mus. Stutchbury; Philippine Archipelago (young specimen), Mus. Cuming. According to Spengler, on the Coromandel and Malabar coasts.

_General Appearance._--Shell depressed, sometimes much depressed: orifice elongated, rhomboidal, but little toothed; surface smooth, but in old specimens sometimes with the walls slightly folded longitudinally. The radii are rather narrow, with their summits oblique; in old specimens their summits are rounded, and their whole surface finely ribbed parallel to the basis. Colour, in old specimens dirty brown, tinged with violet, sometimes in longitudinal bands, and with whiter irregular marks in the upper parts owing to disintegration: in young specimens the walls are regularly banded longitudinally, with violet-brown and dirty white; the radii being generally of a paler dirty red or violet. Basal diameter of largest specimen .9 of an inch.

_Scuta_, externally rather smooth; internally, articular ridge prominent, reflexed, with the lower edge hollowed out so as to be slightly hook-formed: adductor ridge small; there is a slight pit for the lateral depressor. _Tergum_, with the spur bluntly pointed, placed at about its own width from the basi-scutal angle; there is no longitudinal furrow, only a slight depression; carinal margin arched and protuberant: internally, articular ridge extremely prominent, running down in the direction of the middle of the spur: crests for the tergal depressores well developed.

_Parietes_, with the pores rather large; the internal lamina is very strongly ribbed, the ribs being but slightly denticulated at their bases: the parietal pores do not appear to be crossed by transverse septa: sheath closely attached to the walls. The radii have jagged oblique summits forming an angle of about 45° with the horizon; in old specimens they become more oblique and narrow: and are then very remarkable from their summits being arched and rounded, with a crenated edge, and with their whole surface transversely ribbed in horizontal lines; this is likewise the case with the recipient furrow in the opposed compartments: in young specimens the radii are externally quite smooth: the septa on the sutural edges are bluntly denticulated; the interspaces being filled up solidly. The alæ have their summits oblique, but much less oblique than the summits of the radii; their sutural edges are very finely crenated.

_Basis_ thin, either quite solid, that is, not permeated by pores, but only furrowed in lines radiating from the centre, or permeated by pores towards the circumference, the pores being of very small diameter;--so that we here have an important character variable within the limits of the same species. Base flat, and this holds good, as remarked by Spengler, even when the specimens are attached to cylindrical pieces of wood.

_Animal's body_ unknown.

_Affinities._--In the basis being sometimes permeated towards the circumference by pores, and by the colouring (the other species in this and the next section being dirty white), _B. patellaris_ has almost as strong a claim to be ranked in the last as in the present section: in the rounded summits of the radii, and in the state of the basis, it, perhaps, shows more affinity to _B. improvisus_ than to any other species; it is, however, almost equally allied to _B. glandula_.

27. BALANUS CRENATUS. Pl. 6, fig. 6 _a_-6 _g_.

B. CRENATUS. _Bruguière._ Encyclop. Method. (des Vers) 1789.

LEPAS FOLIACEA, _var. a_. _Spengler._ Skrifter af Naturhist. Selskabet, b. i, 1790.

---- BOREALIS. _Donovan._ British Shells, Pl. 160 (1802-1804).

B. RUGOSUS. _Pulteney_ (?) Catalogue of Shells of Dorsetshire, 1799.

---- ---- _Montagu_ (?) Test. Brit. 1803.

---- ---- _Gould_ (!). Report on Invertebrata of Massachussetts (1841), fig. 10.

B. GLACIALIS (?) _J. E. Gray._ Suppl. Parry's Voyage, 1819.

B. ELONGATUS (!), CLAVATUS (!), _Auctorum variorum_.

_Shell white: radii with their oblique summits rough and straight. Scutum without an adductor ridge: tergum with the spur rounded._

_Hab._--Great Britain, Scandinavia, Arctic Regions as far as Lancaster Sound, in 74° 48′ N. (Mr Sutherland); Behring's Straits (Captain Kellett); United States; Mediterranean; West Indies, (Mus. Brit.); Cape of Good Hope, (Mus. Krauss). Generally attached to shells and crustacea in deep water; sometimes to ships' bottoms. Very common.

_Fossil_ in glacial deposits of Scandinavia and Canada, Mus. Lyell; in the mammaliferous, and Red, and Coralline Crags, Mus. S. Wood, J. de C. Sowerby, Bowerbank; Miocene formation, Germany, Mus. Krantz.

I find, in most collections, this species confounded with _B. balanoides_; I have even seen the two species, placed by Leach, on the same tablet in the British Museum: _B. balanoides_ is, moreover, generally confounded with _Chthamalus stellatus_; nor has any one hitherto separated the present species from _B. improvisus_. On the other hand, trifling varieties, both of _B. balanoides_ and _B. crenatus_, have commonly been considered as specifically distinct. From these facts it will be seen in what confusion our commonest British species of Balanus have been left. After due deliberation, I have little doubt that this is the _B. crenatus_ of Bruguière, and probably the _B. rugosus_ of Montagu, but this latter author omits all reference to the really important diagnostic characters between this species and _B. balanoides_. The _B. crenatus_ is certainly the _B. rugosus_ of Dr. Aug. Gould. In various collections, I find specimens of _B. crenatus_, when coming from the arctic regions, called _B. glacialis_, _arcticus_, and _borealis_; though I have not met with an authentic specimen of the _B. glacialis_ of Gray ('Supp. Parry's Voyage,' 1819, p. ccxlvi), I have little doubt that it would prove to be the present species.

_General Appearance._--White, usually of a dirty tint, from the yellowish or brownish persistent epidermis: conical, generally (fig. 6 _a_) with the parietes rugged and irregularly folded longitudinally; but sometimes much depressed and extremely smooth (6 _b_); often cylindrical and very rugged; occasionally club-shaped (6 _c_), the upper part being much wider than the lower: specimens in this latter condition sometimes have extremely narrow parietes, like mere ribs, and wide radii. The orifice in the cylindrical varieties is often most deeply toothed. The radii are generally narrow, and have jagged oblique summits; but not infrequently they are so narrow as to form mere linear borders to the compartments. The orifice is rhomboidal, passing into oval, either very deeply or very slightly toothed.