278 
The American Geologist. 
May, 1890 
of concentric strite, one set very fine and crowded, the other 
much coarser. 
Length, 29 mm. ; greatest width, (measuring from the pos- 
terior extremity of hinge to the basal margin) 17.5 mm.; 
width at the beaks, 12 mm. ; greatest convexity of the two valves 
9 mm. 
This species should be compared with M. modiolaris Conrad, 
M. concentrica H. and W., and M. subtruncata of this paper. 
From the first it differs in having the basal margin convex in- 
stead of sinuate, the anterior end not lobate, a somewhat dif- 
ferent outline, and in being both smaller and comparatively 
more ventricose. Similar differences distinguish it from the 
second, and to them may be added that in that species the 
concentric furrows are mainly restricted to the cardinal and 
posterior regions of the shell. In 31. subtruncata the basal 
margin is straighter, the posterior end more obliquely truncate 
and the beaks more prominent. The surface is also without 
the strong concentric furrows and the outline generally dif- 
ferent. 
Position and locality : Rare in the lower beds of the Cincinnati 
group, at Covington, Ky., at an elevation of between 100 and 150 ft. 
above the Ohio river bed. 
Modiolopsis pulchella, n. sp. 
Fig. 6. Modiolopsis pulchella, n. sp., Utica slate horizon of the Cin- 
cinnati group at Covington, Ky. a. view of the only specimen seen. 
b and c. end and cardinal profile views to show convexity. 
Shell of medium size, moderately convex, transversely sub- 
ovate widest posteriorly, the greatest height and length, re- 
spectively, as five is to nine. Cardinal margin straight behind 
