OF DENISON UNIVERSITY. 
35 
than the length of the valve, nevertheless we dislike to attempt to dis- 
tinguish it from a species confessedly founded on a single imperfect 
ventral valve. Our specimen, however, has no spines and a com- 
pound dischotomy of the striae. Sandy layers of congl. I, Dug- 
way,” near Granville. 
Chonctes logani, Nor. and Pratt. 
Plate VII, Fig. 22; Plate III, Fig. 12 ?) 
In Fig. 22, Plate VII, the radiating costae are not distinct enough, 
while the specimen figured on Plate III may prove to be C. multicos- 
ta, Win. C. logani seems to be distributed throughout the series up to 
congl. II, at least. 
The confusion introduced into this genus by identifying this spe- 
cies with C. illinoisensis, has been corrected by Prof. Winchell. 
Chonetes illinoisensis, Worthen. 
(Plate III, Fig. 21.) 
Rather large for the genus, transversely semioval ; moderately 
convex ventrally ; length between two-thirds and three-fourths the 
width ; hinge lins nearly equal to greatest width, with five or six small 
oblique spines on either side of the inconspicuous beak ; ears some- 
what flattened; nearly rectangular; front -margin a broad curve ; sur- 
face of ventral valve rather evenly convex, highest near the middle, 
casts showing a strong mesial septum; d(')rsal valve gently concave, 
with distinct cardinal' eet . Surface ornamented with about too bi- 
furcating, thread-like striae. Length 7 mm ; width ii mm. Our speci- 
mens rarely attain the size of the western ones, though often much 
larger than the above measurements. 
Found in the sandy rock above congl. I; also forty feet or more 
below this horizon at Moot’s run. The spines of- this species are much 
more slender and curved than in S. scitula. 
