Willistox.] Mosasaurs. 209 



dreds of specimens of Mosasaurs taken from the Kansas chalk 

 previously and since, no other specimen has been found, I be- 

 lieve, that can be referred to this genus. The species remains 

 as a problem which I fear will not be fully solved soon. 



RESTORATION OF THE KANSAS MOSASAURS. 



In plate lxxii are given restorations of the three well-defined 

 •types of Mosasaurs from the Kansas Niobrara Cretaceous — 

 Clidastes, Platecarpus and Tylosaurus. They are based exclu- 

 sively upon the material in the University of Kansas museum, 

 and have been drawn with the greatest care. But very little 

 about them is in any ways conjectural. 



Clidastes is restored from a single specimen, discovered by 

 myself on Butte creek, in Logan county, in the summer of 1891. 

 It is, I believe, the most perfect specimen of a Mosasaur in any 

 museum of the world. Another specimen, nearly as complete, 

 of Clidastes tortor, collected by the late E. P. West two or three 

 years previously, has offered some suggestions in the arrange- 

 ment of the bones. The specimen of C. velox lacks some of the 

 terminal phalanges of the front paddle, and many of the hind 

 paddle ; it is, therefore, not certain that these parts are correct 

 in all details. That there could have been many more or less 

 phalanges than what- are figured, is impossible, since the ones 

 preserved largely determine the number that are missing. 



Platecarpus is based chiefly upon a single specimen, compris- 

 ing the nearly complete disarticulated skull and a connected 

 series of the vertebrae to beyond the middle of the tail, the sixty- 

 fifth, together with the pectoral and pelvic girdles and many of 

 the bones of the limbs. All the limb bones are present in other 

 specimens of the same species. The position of the digits of 

 the front paddle has been determined by the paddle of P. ictericus 

 figured in plate xliv ; that of the hind paddle by the figure 

 given by Marsh. 63 As in Clidastes, some of the digits may have 



63. American Journ. Sci. 



