176 Cincinnati Society of Natural Fitstory. 
ventral half, with point of greatest convexity very near the center; 
surface sloping rapidly from this point to the ends; cardinal slope 
flattened, triangular. Tubercle small, but distinct. Left valve 
represented by only one small individual. In this the surface is 
moderately convex and a little the most convex in the lower half. 
A faint swelling is noticeable along the posterior half of the dorsal 
edge. Surface smooth, apparently impunctate; specimens silici- 
fied. 
This species differs from the preceding in a being a little less 
oblique, in having the ventral region of the right valve more 
tumid, the extremities of the hinge line simply angular instead of 
produced spine-like, and in having only one pit on each side of 
the ventral overlap. The triangular shape and flattened appear- 
ance of the cardinal slope is also diagnostic. Z. divia, White, is 
closely related, but differs in the outline. 
Position and locality: Siliceous limestones occurring near the 
top of the Trenton, at Danville, Ky. The species is rather rare, 
only six examples having been found. 
LEPERDITIA APPRESSA, DN. Sp. 
Plate XT, Laes. SiGe nO ea 
This species is closely related to the two preceding, and as its 
characters are shown very well in the illustrations, a detailed 
description is scarcely necessary. It differs from both Z. “inneyz 
and ZL. ¢umidula in being considerably shorter, rounder, less 
oblique, and much less tumid. There is a well-defined swelling 
along the dorsal edge as in ZL. linneyz. The flange, though all the 
examples seen are larger, is narrower than in either of those spe- 
cies. 3 
Sen f Left valve; length, 13.8 mm.; height, 9.8 mm.; thickness, 2.5 mm. 
: \ 66 6 (3 Pi teve) 6é ce TES 66 66 BIG a & 
Position and locality: Near top of Trenton limestone, at Dan- 
ville and Harrodsburg, Ky. 
LEPERDITIA CACIGENA, S. A. Miller. 
PAGO XA ES. HOG, WO, Cente 
Leperditia cecigena, S. A. Miller, Jour. Cin. Soc. Nat. Hist., Vol. 
TY 3p. 262, plova, ies. sa: ; 
The original illustrations of this species being rather unsatisfac- 
tory, I take this opportunity to offer more reliable figures of two 
