JOURNAL AND PROCEEDINGS. 95 
the numerous teeth, especially in old individuals ; yet the 
writer has known instances where orbicular forms, Cuculea 
Pectunculus for example, were actually mistaken for a species of 
Cardium. The hinge lines widely differ as anyone may see. Up- 
wards of 200 species in a fossilized state occur from the Silurian 
to recent times. 
