AVilliston.] Mosasaurs. 199 



sufficient for generic separation. I am not inclined to agree 

 with him, in the absence of other important differences. Should 

 it be deemed sufficient, however, the name Edestosaurus cannot 

 be used for this genus to include C. velox, since C. dispar is the 

 type of Edestosaurus. 



Of the identity of C. affinis Leidy, I have no doubt. The fig- 

 ures and descriptions given by Leidy agree perfectly, except that 

 he describes the back teeth of C. affinis as having the enamel 

 strongly striated, with the surface presenting evidences of sub- 

 division into narrow planes. The differences from the actual 

 condition of our specimens in this particular are so slight that 

 I do not think the character has any weight. 



In the paper cited above, Williston and Case expressed the 

 opinion that C. pumilus Marsh is identical with C. velox. Mer- 

 riam, who has examined specimens since then, would accept the 

 species as distinct. "C. pumilus Marsh, zeichnet sich besonders 

 durch seine geringe Grosse aus, welcher Eigenschaft wohl einer 

 specifischer Werth beizulegen ist, weil man sonst annehmen 

 mtisste, das Individuen mit der geringen Schadellange von 22 

 cm. zu derselben Species gehoren wie die grossen Exemplare von 

 C. velox." 61 



Nevertheless, it is a question of considerable moment how 

 much specific weight can be placed upon size alone. Not a 

 single character given by Marsh (the structure of the quadrate, 

 basioccipital, etc.) is constant for the species. The only differ- 

 ence is size, so far as I can ascertain, after the most careful 

 scrutiny of the various specimens in the museum. Possibly the 

 jaws are more slender, and the articulation more oblique, but, 

 if so, there must be other species which are intermediate in 

 these characters, yet unnamed. Leidy (1. c, supra) expressed 

 his views of the specific value of size as follows : " It is a ques- 

 tion of some importance how far difference in size among the 

 Mosasauroids may be a test of difference of species. Among 

 the numerous remains of these animals which have been dis- 

 covered, I have never yet observed any which presented any 



61. Paleontographica, Ueber die Pythonomorphen, etc., xli, 35. 



