69 
2. CnoNETES CORONATA, Conrcicl. 
Chonetes sordkla ? Sowerby, 1840, Traus. Geol. Soc. London, V (2), pi. 53, bg. 5 and IG. 
Strophomena carinata (for coronata) . Conrad, 1842, Journ. Acad. Nat. Sc. Pldladelpbia, 
Till, p. 257. 
,, Sljrtalis, Idem, 1842, Hid., p. 254, pi. 14, fig. 1. 
Chonetes coronata, J. Hall, 18G7, Pal. N. York, IV, p. 133, pi. 21, fig. 9-12. 
Shell transverse, snbelliptic, hinge line of the same length or sometimes 
a little shorter than the width. Ventral valve generally convex, slightly 
sinnated in the middle, ears depressed. Dorsal valve more or less concave, 
and following at a slight interval the course of the opposite valve. All the 
surface is ornamented with a very large nnmljer of delicate radiating ribs, 
subeqnal, increasing by forking or by interposition. In well-preserved 
individuals these small ribs are traversed by concentric groAvth- lines, 
principally towards the margin. 
The hinge-line of the ventral valve is provided on either side of the 
beak with five to seven sj^iniform tubes, of which usually two or three only 
are visible. The area is triangular hut very arched. 
The interior of the ventral valve, of which I have been able to examine 
the impression only, shows two rather strong and diverging dental plates, andi. 
a thin, very short, median septum ; on either side of this may he seen a small 
impression of elongate oval outline, formed by the adductor muscles, while the 
impressions of the cardinal muscles are scarcely visible ; beyond these 
impressions and up to within a certain distance of the outer margin, bounded 
by a slight inflation [ridge] parallel to the margin, all the inner surface is 
covered by small spines, which produce on the mould small pits similar to 
pin pricks. The inflated portion itself of the margin only carries a small 
number of these little pits on its inner portion, while the marginal portion 
is ornamented by very delicate radiating striae, which give it a fringed 
appearance. 
I have not had an opportunity of examining the internal structure of 
the dorsal valve. 
Ohservation. — I am almost certain that this species, which is quite 
distinct from C. Ilardrensis in shape, size, and the great number of ribs, is 
identical with C. sordkla, Sowerby ; hut as I am without the facts required 
to settle this question, I prefer not to attempt it. 
