180 Cincinnati Society of Natural Lfiistory. 
The outline of the specimens for which the above name is pro- 
posed agrees very nearly with that of /. armata, Walcott, the chief 
differences being that in that species doth extremities of the long 
hinge-line are produced into short spines, while in this only the 
anterior end is prolonged; in Walcott’s species the ventral margin 
is less convex and therefore more nearly parallel with the back, 
and the two ends more narrowly rounded in the lower half. The 
eye tubercle in /. Kentuckyensis is smaller and farther removed 
from the antero-dorsal angle, while the ventral tubercle or spine is 
much smaller, directed backward, and does not preject beyond 
the ventral edge. The valves are also less and more evenly 
convex, there being no pronounced swelling above the spine. A 
row of minute pits along the ventral edge, and a narrow flange all 
around the free margins, two features not noticed in /. armata, aid 
in separating the species. 
Ll. Kentuckyensis should be compared also with Kalmodin’s 
Leperditia tuberculata, GAfvers, K. Vet.-Akad. Férh. (1879) 1880, 
which also has a sharp ventral spine. 
Position and locality: In the Birdseye limestone, upper beds, at 
several localities in Mercer county, Ky., and at Frankfort, Ky. 
ISOCHILINA AMIANA, Nl. Sp. 
IAOER OC SHIR WPA Oh Dy G. 
Size of vather large right valve: Length, 5.1 mm.; height, 3.0 
mm.; thickness, 1.13 mm. 
Valves rather small, obliquely ovate, produced and widest pos- 
teriorly; ventral edge moderately convex, rounding neatly into 
the anterior margin; back straight, rather short, obtusely angular 
at the extremities. Posterior edge most curved in the lower half. 
Antero-dorsal region generally somewhat elevated, with a V- 
shaped or illy defined depression just behind the elevation. In a 
few specimens two faintly marked tubercles on each side of the 
depression add much to its definition. In others over half of the 
dorsal slope back of the anterior swelling may appear depressed. 
Central portion of valves strongly convex. Flange narrow, smooth, 
usually of nearly uniform width and extending all around the free 
margins ; rarely obsolete at the anterior end. Surface impunctate, 
occasionally exhibiting a few obscure radiating lines over the cen- 
tral portion of the valves. 
