343 



a palatine bone with teeth of an undoubted raosasauroid, that led me into the 

 error of supposing it belonged to the same animal. This suggested the idea 

 that the specimen originally referred to Atlantochelys Mortoni likewise be- 

 longed to a Mosasaurus. The error was easy at a time when the limb-bones 

 of none of the mosasauroids were known, and when it was even doubted 

 whether these reptiles possessed hinder limbs. My determination was con- 

 curred in, not only by Professor Cope, but also by Professor Agassiz, after I 

 had exhibited to him the different specimens and their associates.* It was 

 only after I had had the opportunity of seeing the nearly complete fore-limbs 

 in the skeleton of Clidastes propython, described by Professor Cope, that 

 I suspected my reference of the specimens of humeri above indicated was 

 incorrect. 



CYNOCERCUS I 



Cynoceecus incisus. ? . 



Cope : Pr. Am. Phil. Soc. 1872, 309. 



Remains probably belonging to this species described page 269, and 

 represented by Figs. 17 to 21, Plate XXXVI. From the Cretaceous 

 of Kansas. 



Mosasauria. 



MOSASAURUS ? 



Mosasaurus 1 



See page 279. Represented by Fig. 15, Plate XXXVI. From the Cre- 

 taceous of Nebraska. 



TYLOSAURUS. 



Tylosaurus dyspelor. 



Marsh : Am. Jour. Sc. 1872, 147. 



Liodon dijspelor. Cope : Pr. Am. Phil. Soc. 1870, .172, 574 : 1.^71, 10!), 2S0; Hay- 

 den's Eep. Geol. Sur. Wyoming, 1871, 410 ; Hayden's Rep. Geol. Sur. Montana, 

 1872, 333. 



Rhinosaurus dyspelor. Marsh : Am. Jour. Sc. 1872. 



Rhampliosaiiriis. Cope: Pr. Ac. Nat. Sc. 1872, 141. 



See page 271. Represented by Figs. 1 to 11, Plate XXXV. From the 

 Cretaceous of New Mexico and Kansas. 



*I do not introduce the names of these naturalists as an apology for my error, but 

 rather to show that able authorities are liable to the same mistakes under the same 

 circumstances. 



