OF DENISON UNIVERSITY. 
53 
Crenipecteji suh-cardiformis , sp. n 
(Plate Vil, Figs. 4-5 ) 
Cf. Aviculopecien caroli, Winchell, 1863, pars. ? 
[Wrongly quoted above as C. tumidus.] 
We have been caused a great deal of perplexity by this species, 
which occurs by scores in our collection. It is chiefly restricted to a 
zone about 40 feet below congl. I, though it ranges upward to a hori- 
zon just beneath it in comjiany with streblopteria media. Aviculopec- 
ten caroli, Winchell, would not be considered in this connection were 
it not (or the statement made by Prof. Winchell, in 1870, that it was 
found at Granville, but that the specimens from that locality “ were 
all right valves, and are much flatter than tvpical specimens of the 
same valve.” On the whole it may be safer to regard our form as a 
distinct species unless a comparison of types proves this not to be the 
case. Shell of medium or small size, nearly circular, height and 
length equal, with well-defined and depressed ears. Left valve very 
ventricose, hinge slightly shorter than extreme length ; lower margin 
a nearly circular curve intersecting the auricular margin at about two- 
fifths the distance from the hinge to the lower margin; anterior ear 
rather large, greatly depressed below the adjacent portion of the body, 
from which it is separated by a sudden deflection ; posterior ear less 
sharply defined, but nearly equally as large and not separated by a 
well-defined sinus from the body, depressed ; beak high, but incurved 
and acute, projecting slightly beyond the hinge ; greatest convexity 
near the union of the upper and middle thirds; surface marked by 
from thirty to forty strong, very irregular, radiating costas, alternate 
ones being generally smaller and originating by implantation or, more 
rarely, bifurcation ; these costae are crossed by fine, close, but irregu- 
lar concentric striae, which do not cross the larger costae, and distant 
undulations; the anterior ear bears about six costae, while the poste- 
rior ear is nearly smooth, but exhibits more plainly the concentric 
striae; rarely two small costae occupy the space between the larger ra- 
diating ribs. The right valve is very flat and nearly without markings ; 
the hinge is longer than or equal to the greatest length and the ears 
are very large ; and nearly equal ; the anterior ear is set off by a deep 
depression from the body and the valve is provided with a deep bys- 
