Described paifc 311, and represented .l)y Figs. 4 to 6, Plate XVII. From 

 the Carboniferous formation of Kansas, Nebraska, and Illinois. 



CESTRACIONTIDiE. 



ACRODUS. 



ACKODUS HUMILIS. 



Leidy : Pr. Ac. Nat. Sc. 1S72, 103. 

 Described page 300, and re|irescntc(l by Fig. 5, Plate XXXVII. From 

 the Cretaceous limestone of New Jersey. 



AcEODUS Emmonsi. 



Leidy : Pr. xVc. Nat. Sc. 1S72, 103. 



Acroclus. Emmous: North Carolina Geol. Sur. 18.58, 211, Fig. 97. 



Attributed by Professor Emmons to the Miocene of North Carolina. 



PTYCHODUS. 

 Ptyohodus Mortoni. 



Agas.siz: PoIssods Fossiles III, 1833-'43, 158, Tab. 25, Figs. 1 to 3; copied in 

 Figs. 773, 773rt, of Dana's Manual of Geology. Leidy : Pr. Ac. Nat. Sc. 1808, 

 205. 



Palate-boiie of a fish ? Morton : Syn. Org. Rem. Cret. Group, 1831, Plate XVIII, 

 Figs. 1, 2. 



Described page 295, and represented by Figs. 1 to 14, Plate XVIII 

 From the Cretaceous of Kansas, Mississippi, and Alabama. 



Ptychodus occidentalis. 



Leidy : Pr. Ac. Nat. Sc. 1868, 207. 

 Described page 298, and represented by Figs. 7, 8, Plate XVII, and Figs. 

 15 to 18, Plate XVIII. From the Cretaceous of Kansas. 



Ptychodus Whippleyi. 



Marcou : Geology North America, 1858, 33, Plate I, Fig. 4. 

 Described page 300, and represented by Figs. 19, 20, Plate XVIII. 

 From tlie Cretaceous of Texas. 



Ptychodus polygykus. 



Agassiz : Poissous Fossiles III, 1833-'43, 150. Dixon : Geol. Sussex, 1850, 363. 

 Gibbes: Jour. Ac. Nat. Sc. 1810, 290, Plate XLII, Figs. 5, 0. Leidy: Pr. Ac. 



Nat. Sc. 1808, 208. 



From the Cretaceous of Alabama. 



