io6 



CES TRA CIONTID^. 



" Two dorsal fins, an anal ; nasal and buccal cavities con- 

 fluent. Teeth obtuse, several series being in function." 

 (Giinther.) 



Ptychodus, Ag. 



Poissons Fossiles, t. iii., p. 56. 



Ptychodus Whippleyi, Marcou. 



Geology of North America, 1858, p. 33, 



Represented by a tooth from the cretaceous of Cement 

 Gulch, almost identical with the specimen described by Dr. 

 Leidy from the cretaceous of Texas. (Cont. to Ext. Vert. 

 Fauna, p. 300.) 



