ORISKANY FAUNA OF BECRAFT MOUTSTTAIN 109 



21 Posterior view of the same specimen showing the sub- 



apical groove 



22 An enlargement of the external ornament. x6 



23 A smaller example Avith more strongly developed median 



carina 



Strophostylus expansus Hall 



Page 30 



24 An upper view of a characteristic specimen 



Diaphorostoma ventricosum Hall 



25-28 Views of various specimens showing the general aspect of 

 the shell in this fauna 



Platyceras cf. gebhardi sp. nov. 



Page 80 



29 Lateral view of an internal cast of this species 



