Mandibles with three teeth; maxillæ narrow, bearing only four or five pair of spines.

Males, two, lodged in cavities on the under sides of the scuta; pouch-formed, with four unequal, rudimentary valves: no mouth: cirri not prehensile.

Algoa Bay, South Africa. Attached to Sertularia and Plumularia. British Museum.[55]

[55] I am greatly indebted to Mr. Bowerbank for specimens of this extremely interesting species; also to Mr. Morris, to whom Mr. Bowerbank had given some of the original specimens.

FEMALE.

Capitulum oblong, with the upper portion much produced; valves, 14, thick, naked, closely locked together, irregularly clouded with pale crimson; the membrane connecting the valves is not furnished with spines. On most of the valves there are furrows and ridges diverging from the umbones, and the lines of growth are plainly marked: in the valves of the lower whorl, the umbones are slightly protuberant.

Scuta, convex, unusually thick, oblong, quadrilateral, with the occludent margin the longest; lateral margin slightly hollowed out. The umbo (and primordial valve) is situated at the uppermost point of the valve, and consequently the growth is exclusively downwards. On the under side ([Pl. VI], [figs. 1 b´ and 1 c´]), in about the middle of the valve, there is a pit (a) for the adductor scutorum muscle, the depth and distinctness of which varies a little; above the pit, and between it and the apex, there is a transverse, oblong, deeper depression (b), within which, the male is lodged. A small portion of the apex of the valve projects over the terga.

Terga, large, nearly equalling the scuta in area, flat and sub-triangular; the scutal margin is not quite straight. The apex of the valve is thick and solid, and must have projected freely for a length equalling one third of the occludent margin.

Carina, laterally broad, angularly bent; slightly widening from the apex to the base; internally, deeply concave. The position of the umbo varies, in young specimens it is seated at the uppermost point, and consequently in such there is no upward growth; in older specimens, from the junction and upward production of that part on each side of the valve, which I have called in fossil specimens the intra-parietes, the valve is added to above the umbo, but to a lesser degree than in S. vulgare. Slight ridges separate the roof from the parietes, and the parietes from the intra-parietes.

Rostrum, minute, narrow, widening a little from the apex downwards, inserted like a wedge between the umbones of the rostral latera, and hardly projecting above their upper margins, so as to be easily overlooked: internally concave.