OF THE UNITED STATES. 67 
Veniiia, (S.G. M.) 
Generic character. An equivalve bivalve; hinge with three 
robust cardinal teeth in each valve, and an elongated, thick, 
lateral tooth on the posterior side, similar to that of Unio: an- 
terior muscular impression profound. 
V. Conradi, (S. G. M.) Pl. vin, fig. 1 and 2. 
Specific character. 'Trigonal, ventricose, thick, concentric- 
ally sulcated; beaks long and incurved. 
Diameter, one inch and a half. 
This singular marine shell, so different from any of the 
hitherto known genera, was discovered at Arneytown, 
New Jersey, by my friend Mr. T. A. Conrad, in whose 
name I gladly introduce it to notice. He has since found 
it at Prairie Bluff, Alabama. It is possible that the As- 
TARTE frigonalis, of Sowerby, (Min. Conch. pl. ceccxliv, ) 
may belong to this genus. 
CYTHEREA. 
C. excavata, (S.G.M.) PI. v, fig. 1. 
Specific character. Suborbicular, compressed; posterior 
slope deeply excavated ; posterior side with an obsolete fold ; 
margin angular. 
Diameter, about an inch and a half. 
Found by Mr. T. A. Conrad, at Arneytown, New 
Jersey. 
LUTRARIA ? 
Casts are occasionally found seemingly belonging to this 
genus. One from the marl of Delaware strongly resem- 
