235 
which is somewhat reflected and cuspidate ; and constitutes, as it were, 
the apex or summit of the pyramid : the back, or that part of the valve 
proceeding from the margins, rounded : the opposite side flat, consisting 
of the hinge and foramen described. The other valve semicircular, 
moderately convex, broad ; its beak prominent, pointed, and incurved 
over the base of the foramen.” 
The specimen represented Plate X\ I. Fig. \J , differs from that figured 
by Mr. Martin, only in the beak of the conic valve not being so much 
reflected. On the upper part of this figure is the semicircular valve, 
with the convex wave on its back, a, terminating forwards in the pro- 
minent, pointed beak, incurved over the base of the foramen. On the 
lower part is the conic valve, which has on its back part, but which could 
not be here shown, a deep rounded sinus, its base joining the base of the 
convex wave on the semicircular valve at a, and terminating in a point at 
the bottom, where it meets the point of the perpendicular triangular 
foramen at b, in the apex, or what must rather be considered as a beak, 
though not so formed. 
This ingenious naturalist observed, that the species A. suhconicus 
united this species with the more common straight-hinged perforated 
anomitee ; but added, that in another shell, which he had not yet named 
or described, the hinge is still less ; and the beak of the large valve, 
instead of being straight, is somewhat incurved, and therefore more 
strictly united the species. As Mr. Martin’s collection is now dis- 
persed, there is little reason to expect that the figure of this shell will 
be published ; it is therefore with pleasure I find myself able to give a 
representation of a shell which seems to possess all the characters of 
that of which he has spoken. 
This shell, Plate XVI. Fig. 16, is of a roundish trigonal form, with 
two convex, longitudinally -furrowed, valves; the furrows being rounded. 
The hinge straight, extended, and very patulous, with a large triangular 
pit or foramen, between the beaks of the two valves. The beak of the 
large valve, at the point of the foramen, at h, unlike that of the pre- 
