196 University of Kansas Geological Survey. 



foramen of moderate size, situated within the parietal bone. 

 Facial surface of parietal elongate, the sides nearly parallel, 

 emarginate posteriorly. Quadrate relatively small, the supra- 

 stapedial process reaching to about the middle of the bone. 

 Expanded portion of the palatine elongate. Vertebrae with 

 functional zygosphenes. Vertebrae from 117 to probably not 

 more than 125 in number. Thoracic vertebras eleven or twelve, 

 lumbo-dorsals twenty-four or more, pygal caudals seven. 

 Chevrons long, coossified with the centra. Tail much com- 

 pressed, the spines elongated posteriorly. Limbs small ; arm 

 and leg bones short and expanded. Phalanges not more than 

 six in number in any digit. Fifth finger divaricate and shorter 

 than the fourth. Hallux rudimentary or wanting. Hind limb 

 much smaller than the anterior one. Coracoid emarginate or 

 entire. Ischium but little expanded distally, pubis with a proxi- 

 mal anterior process. 



These characters are based upon a nearly complete specimen 

 of C. velox and the larger part of one of C. tortor. The complete 

 tail is known only in C. velox, and hence it is possible that the 

 dilatation may not be present in other species. 



The genus Clidastes, as first described by Cope, was based 

 upon two dorsal vertebras of C. iguanavus, the type species, 

 from New Jersey. Shortly afterward, however, he gave a full 

 generic description, as derived from an unusually good speci- 

 men of an allied species, C. propython, from Alabama. Only a 

 little later, Marsh described a genus, which he called Edestosau- 

 rus, from Kansas, but without giving any really distinctive char- 

 acters from Clidastes. The genus Edestosaurus has now been 

 rejected by all writers on the Mosasaurs, save its author. It 

 seems hardly necessary to point out the identity. The only 

 distinctive character the author gave for his genus was the in- 

 sertion of the pterygoid teeth, and even this character he modi- 

 fied later — "Palatine [sic] teeth more or less pleurodont." 60 



The genus is certainly very closely allied to Mosasaurus, but, 

 I believe, shows sufficient distinctive differences to justify its 

 existence. The form of the animal is elongated, as in that 



60. American Journ. Sci., ill, June, 1872. 



