PELECYPODA—ANOMALODESMACEA. 531 



466. P. petrosa (Conrad). (Fig. 720.) Eocenic. 



Ventricose anteriorly. Radii sharp, numerous. 

 Aquia of Maryland. 



Fig. 720. Phenacomya petrosa, left and cardinal views, Xf- (Md. Surv. ) 



CXXVIII. Anatimya Conrad. 



Oblong. Anterior side with concentric sculpture ; posterior 

 with concentric and radiating ribs. Cretacic. 

 467. A. anteradiata Conrad. (Fig. 721.) Cretacic. 



Fig. 721. Anatimya anteradiata. (After Well er, Pal. N. J., IV.) 



Beaks scarcely elevated above hinge line, pointing posteriorly. 

 Valves depressed-convex. Margins subparallel. 



Ripleyan of New Jersey (Woodbury, Wenonah), Mississippi. 



CXXIX. Liopistha Meek. (Includes Cymella Meek.) 



Equivalve, oval, thin, inflated. Valves gaping and compressed 

 posteriorly, concentrically or radially striated. Beaks prominent, 

 incurved. Hinge inflected along its entire length. Cardinal teeth 

 two, projecting directly outward from beneath the beaks. Liga- 

 ment sunken, partly external. Cretacic. 



The typical Liopistha has the shell ornamented principally by 

 strong radial ribs, while in the subgenus Cymella the chief sculp- 

 ture is the large, strong, regular concentric undulations which are 

 crossed by only a few radiating markings. 



