rica. 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.

_Upper Latera_ (fig. 1 _a_)