PEEECYPODA— PRION ODESMACEA. 475 



Fig. 634. a-c, Exogyra columbella, lower umbonal and upper views ; d, E. 

 Iceviuscula, lower valve. (After Stanton.) 



Fig. 635. a, b, Exogyra ponderosa ; c, E. suborbiculata, lower valve. All X Yz> 



(After Stanton.) 



