2M 



ELASMOBRANCHII. 

 PTYCHODUS, Agassiz. 



Polssous fossiles, 1833, III, 150. 



Ptychodus polygyrus, Agassiz. 



Poissous fossiles, III, p. 156 : Gibbes, Journal of the Academy of Philadelphia, 1849, 299, 

 Plate XLII, figs. 5-6 ; Leidy, Proceedings of the Academy of Philadelphia, 1868, p. 208. 



Rotten limestone of Alabama, and Niobrara epoch of Kansas. 

 Ptychodus janevaii, Cope. 



Sporetodus janevaii, Cope, Haydeu's Bulletin of the United States Geological Survey of the 

 Territories, No. 2, 1874, p. 47. 



Niobrara Cretaceous of Kansas. 

 Ptychodus occidentalis, Leidy. 



Proceedings of the Academy of Philadelphia, 1808, p. 207 ; Report of the United States Geo- 

 logical Survey of the Territories, 1873, p. 398, Table XVII, 7-8, XVIII, 15-18. 



Niobrara epoch of the Smoky Hill. 

 Ptychodus mortonii, Agassiz. 



Poissous fossiles, III, p. 158, Plate 25, figs. 1-3. 



Niobrara Cretaceous of the Smoky Hill River, Professor Mudge; Ala- 

 bama ; Mississippi. 



Ptychodus whippleyi, Marcou. 



Geology of North America, 1856, p. 33 ; Leidy, Keport, etc., 1873, 300, Table XVIII, 19-20. 



Niobrara epoch of the Arkansas River, Kansas; also, Colorado and 

 Galisteo, New Mexico. Professor Merrill. 



Ptychodus mammillaris, Agassiz. 



Poissous fossiles, III, p. 151. 



Cretaceous greensand, No. 4, of Delaware. 



Ptychodus papillosum Cope. 



The grinders of this species possess the elevated form of those of P. 

 whippleyi, and are of about the same size. The surface is characterized by 

 the absence of folds or ridges, but is uniformly covered with subecpial areolae 

 or papillae of small size, giving the cementum a shagreened appearance. 



Cretaceous, No. 3, of Colorado, east of the Rocky Mountains. 



