OF DENISON UNIVERSITY. 
79 
GENUS LEPT^ENA, Dalman. 
I. LePT^NA PROLONGATA, Sp. 11. 
( Plate XIII, Pigs. ^ a, b.) 
Shell of medium size, concavo-convex, semi-oval ; hinge line pro- 
longed, exceeding the width of the shell, lateral extremities acutely 
angular. 
Ventral valve, alone known, very convex, highest elevation at about 
one third the distance from the beak to the anterior margin, thence 
curving rapidly towards the anterior margin, and far more so towards 
the posterior margin or hinge line, which is inflected. There is a 
tendency towards a slight mesial elevation. 
Surface marked by fine, close striae, some of which are more prom- 
inent, the spaces between being puncto-striate. Interior of shell also 
striated in the same direction as the exterior surface, the reticulated 
structure of L. transversalis not observed. 
This species is closely related to L. transversalis , from which it dif- 
fers in its larger size, the lateral prolongation of the shell, especially 
along the hinge line, absence as far as known of reticulations among 
the interior striae, and by the tendency towards a mesial fold. From 
Z. sericea it can be distinguished by its great convexity from the ante- 
rior towards the posterior regions. (The specific term is intended to 
suggest the lateral prolongation of the shell.) 
Length, 13 mm.; breadth, 25 mm.; convexity of the ventral valve, 
5 to 6 mm. 
Locality and position. Soldiers’ Home, Clinton Group. 
genus STROPHOMENA. Rafinesque. 
II. Stroppiomena patenta. Hall. 
Shell described in Ohio Pal. Vol. II. 
Locality and position. Soldiers’ Home Quarries, Clinton Group ; 
common. 
III. Strophomena RHOMBOiDALis, Wilckens (sp. ). 
Described in Ohio Pal. Vol. IT; variable. 
Locality and position. Soldiers’ Home and Huffman Quarries, 
Clinton Group. 
