Williston.] Mosasaurs. 195 



MOSASAUKIN^E. 



Mosasaurince Williston, Kans. Univ. Quart., vi, A, 181, 1897. 



Hind limbs tetradactylate. Carpus and tarsus fully ossified, 

 and with not more than six phalanges in any digit. Trunk 

 relatively long, the thorax short, the tail much compressed dis- 

 tally, the chevrons coossified wth the centra. Zygosphenes 

 rudimentary or functional. Humerus with a strong radial proc- 

 ess at the distal end. Prefrontal more or less dilated into a 

 horizontal plate posteriorly. Coronoid large, articulating with 

 splenial on the inner side. Rostrum short, obtusely conical. 

 Quadrate small, with a suprastapedial process of moderate 



length. 



Mosasaurus. 



Mosasaurus Conybeare, in Parkinson, An Introduction to the Study of 

 Fossil Organic Remains, 198, 1S22. 59 



Zygophenes rudimentary or wanting. 



This character, slight as it is, seems to be the only one that 

 is applicable for the differentiation of the species from those of 

 Clidastes. Possibly future knowledge of the forms now known 

 as Mosasaurus may determine other characters that will be of 

 generic value either in the separation of this, or for the erec- 

 tion of others. The genus includes the largest of the known 

 Mosasaurs, while those of Clidastes are either very small or of 



moderate size. 



Clidastes. 



Clidastes Cope, Proc. Acad. Nat. Sci. Phil., 1868, p. 233. 

 Edextosaurus Marsh, Atner. Journ. Sci., i, p. 417, June, 1871. 



Small to medium sized, elongated, and slender. Premaxillary 

 short, projecting but little beyond the teeth, obtusely conical. 

 Teeth faceted upon the outer side, smooth on the inner, or smooth 

 throughout ; fifteen or sixteen in number in the maxillae, sev- 

 enteen or eighteen in the dentary, and twelve to fifteen in the 

 pterygoids. Nares moderately dilated, situated anteriorly. 

 Frontal not emarginated in the middle posteriorly. Pineal 



59. " Mosasaurus, the Saurus of the Meuse, the Maestricht animal of Cuvier. As Cuvier has 

 not yet given it a name, thi3 name is suggested by Mr. Conybeare until he has done so." 



15 — iv 



