3Ionograph of the Crustacea of the Cincinnati Crroiqy. 121 



very slightly above the hinge, and rounding off regularly into the 

 anterior margin ; surface nearly smooth. 



It varies much in form and size : one specimen having length, ^-^-^j 

 inch ; height, —^ inch ; convexity, ^y^ inch ; another having length, 

 ■^^ inch ; height, yf ^ inch ; convexity, y-^-jj inch ; other specimens 

 being both larger and«smaller. 



Found on the east side of Avondale pike, back of Cincinnati, with 

 Odhis hellula, from 360 to 400 feet above low water mark. As this is 

 the only locality known to me, it is the only one I can point out, but 

 it has been found at other places at about the same elevation. It is a 

 rare fossil. 



Fa m ily Leper d it idee. 



Genus Leperditia (Ronault, 1851), as redefined by Jones. 



Animal inclosed in a vertical, bivalved carapace. Carapace inequi- 

 valved ; somewhat resembling a tamarind stone and other legumina- 

 ceous seeds. Carapace valves smooth, convex, horny in appearance, 

 nearly oblong, longer than broad, bean-shaped, inequilatoral, posterior 

 half broadest ; dorsal border straight ; ventral border nearly semi-cir- 

 cular ; anterior and posterior borders oblique above, rounded below, 

 the valve margin passing from each end of the hinge line in an oblique 

 direction downward and outward, to about half the breadth of the 

 valve, where it meets the curved ends of the ventral border, and so 

 forms the more or less angular extremities of the valve, the former of 

 which is narrower and sharper than the latter. 



Valves \mited along their upper (dorsal) borders by a simple linear 

 hinge ; the two extremities of hinge border form angles with the an- 

 terior and posterior borders in each valve. 



The right valve larger than the left, being broader, and overlapping 

 completely the ventral border of the opposite valve, and to some ex- 

 tent its anterior and posterior borders. The overlapping ventral bor- 

 der of the right valve forms a thick, blunt keel to the closed carapace. 



Each valve is somewhat depressed toward the dorsal border ; this 

 border in the left valve is thicker than that of the right, and some- 

 times slightly overrides it. The ventral margin of the left valve 

 is turned suddenly inward, forming a thin plate, projecting into the 

 cavity of the carapace. The line of junction of the inverted border, 

 or ventral plate, and the outer surface of the valve is angular, and 

 bears a slight sulcus and moulding, against which the overlapping edge 

 of the right valve abuts. The dorsal or the ventral profile of the 

 closed valves is elongate, acute oval ; the end view of the closed valves 

 is more or less ovate. 



