82 
PALEONTOLOGY OF NEW-YORX. 
quite distinct; in other cases they are less so, and sometimes there appears only a single 
mesial fold with a depression on each side. 
Fig. 7 a. Ventral valve, with the large elevated beak of the dorsal valve incurved over it. 
Fig. 7 b. Dorsal view of the same specimen. 
Fig. 7 c. Cardinal view, showing the great convexity of the dorsal valve. 
Fig. 7 d. Profile view of the same. 
Position and locality. In the upper limestone of the group at Lockport, Niagara county. 
(Collection of Col. Jewett. State Collection.) 
