343 



a palatine bone with teeth of an nndoubted niosasaiiroid, that led me'^into the 

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

 that the specimen originally referred to Atlantochelys Mortoni likewise be- 

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

 of none of the mosasanroids were known, ;uul when it was even doubted 

 whether these rejjtiles possessed hinder lind)s. My determination was con- 

 curred in, not only by Professor Cope, but also Ijy Prcdessor 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 pro]iijthon, described by Professor Cope, that 

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

 incorrect. 



CYNOCERCUS? 



Cynocercus incisus. ■? 



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



Remains probably belonging to this species described page 2G9, and 

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

 of Kansas. 



Mosasauria. 

 MOSASAURUS ? 



MOSASAURUS % 



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

 taceous of Nebraska. 



TYLOSAURUS. 



Tylosaurus dyspelor. 



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



Liodon dyspelor. Cope : Pr. Am. Phil. Soc. 1870, 572, 574 ; 1871, 109, 280 ; Hay- 

 den's Eep. Geol. Sur. Wyoming, 1871, 410 ; Haydeii's Rep. Gcol. Snr. Montana, 

 1872, 333. 



Rhinosaurus dyspelor. Mar.sh : Am. Jour. So. 1872. 



BUampliosaurus. Cope : Pr. Ac. iSTat. 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 mistaices under tlie same 

 circumstances. 



