PELECYPODA—PRIONODESMACEA. 



405 



108. N. brevifrons Conrad. (Fig. 519.) Cretacic. 

 Radiating lines nearly obsolete. Umbonal ridge rounded. 

 Ripleyan of New Jersey (Cliffwood, Wenonah ?), North Carolina, 



Mississippi. 



109. N. eufalensis (Gabb). (Fig. 520.) Cretacic. 



Fig. 520. Nemodon eufalensis, with cardinal margin enlarged. (N. J. Pal., I.) 



Valves marked with a mesial depression, producing a slight 

 emargination of the base. Radiating striae fine and numerous. 



Ripleyan of New Jersey (Merchantville-Tinton), Georgia, Ala- 

 bama, Mississippi, Arkansas. 



no. N. sulcatinus Evans and Shumard. Cretacic. 



Similar to N. eufalensis in outline but very small (length slightly 

 over ^ inch) and with mesial depression broad and deep. 



Coloradoan : Utah, South Dakota. Montanan : Montana. 



XXXIII. Cucull^ea Lamarck. 



Similar to Area but hinge with short central transverse or 

 oblique teeth and two to five short lateral teeth nearly parallel to 

 the hinge line. Posterior adductor scar fixed to a thin raised plate. 



The subgenus Idonearca includes in general the forms with 

 thicker shells and fewer teeth than the typical Cucullcea. Jurassic 

 -Recent. 



in. C. vulgaris Morton. (Fig. 521.) Cretacic. 



Fig. 521. Cucullcea vulgaris, internal molds. (N. J. Pal., I.) 



Its internal molds differ from those of C. tippana in being more 

 oblique, with longer beaks. 



