FEMALE OR HERMAPHRODITE.

There is only a single specimen in the British Museum, and this had nearly all its valves separated, and many of them in fragments: from its state of decay, I think the specimen must have been dead, when originally collected.

Description.—The capitulum consists of fourteen valves, including from analogy a rostrum.[58] Valves, apparently covered with membrane, bearing some thin spines on the margins; clouded with a fine, though pale, orange tint; surfaces plainly marked with lines of growth.

[58] In my first, and as I thought careful examination of the separated valves (my only materials) of this species, I mistook one of the triangular rostral latera for the rostrum, and hence was unfortunately led into an error in my ‘Monograph on the Fossil Lepadidæ of Great Britain,’ in which I state that the present species has only twelve valves in the capitulum; and I inferred from this, that S. quadratum, S. fossula, &c., had only twelve valves; I still believe this to be correct, but the existence of fourteen valves in S. rutilum and S. ornatum, the recent species to which the above fossils are most closely allied, no doubt is a strong argument in favour of this higher number.

Scuta, elongated, nearly three times as long as broad; apex, pointed; basal margin extremely oblique, forming an acute angle with the occludent margin; the lateral margin is slightly hollowed out, and is separated from the tergal margin by a large rectangular projection or shoulder. The occludent margin is nearly straight; externally, there is a slight ridge running down the middle of the valve, from the apex to the baso-lateral angle; and a second ridge running from the apex to the tergo-lateral angle. The lines of growth do not end abruptly at the tergo-lateral angle, as is the case with S. ornatum and several fossil species, but run up a little way along the tergal margin. The umbo is seated at the uppermost point, and, therefore, the main growth is downwards. There is a large rounded depression for the adductor muscle ([a, fig. 2 a´]), and higher up, opposite the tergo-lateral angle, there is another hollow (b), for the lodgment of the males; this latter is of nearly the same shape as the hollow for the adductor muscle, but rather more conspicuous than it. From the appearance of the under surface of the scuta, it might readily have been thought, that there had been two adductor muscles.

Terga, of large size, longer than the scuta, flat, triangular, with the whole inferior part much produced and spear-like. A portion of the apex, must have projected freely above the sack.

Carina ([Pl. VI], [fig. 2 b´]), simply bowed (i. e., not rectangularly bent), with the umbo (and primordial valve) seated at the upper point; rather massive, narrow, only slightly increasing in width from the upper to the lower end; the two sides are flat, and at right angles to the roof, which is bordered on each side by a rather broad, square-topped ridge (see section [fig. 2 c´]), or the roof may be said to have a square-edged furrow running from the apex to the basal margin, and widening downwards; these two ridges have their lines of growth oblique, and hence have a twisted appearance; the central depressed portion of the basal margin, which is square or truncated, descends lower down than the two ridges. The sides of the valve close to the apex are broad, and consist, as I believe, of intra-parietes, as well as of parietes, but these parts are not separated from each other by ridges, as is commonly the case, more especially with the fossil species. I have described the carina in some detail, on account of its resemblance to that of the cretaceous S. fossula, S. trilineatum, and S. quadricarinatum.

Rostrum, unknown; but one probably existed.

Upper Latera, of large size, elongated, quadrilateral, approaching to diamond-shaped, with the angles rounded, nearly twice as long as broad; almost flat; upper half acuminated, lying between the scuta and terga; the lower half broad, forming a rectangular projection lying between two latera of the lower whorl. The umbo is near the apex, the greater part of the growth being downwards, but the valve is added to a little, round the two sides of the apex; these additions do not take place in the early stages of growth, (as explained under S. vulgare,) and, therefore, they form a depressed rim.

Rostral Latera, almost exactly triangular, curved; basal margin furnished with a just perceptible rim.