AVilliston.] Mosasaurs. 197 



genus, the paddles are of the same structure, and the skull 

 shows very strong resemblances. The presence of functional 

 zygosphenes will at once distinguish the known species. 



Three species of Clidastes have been described from other 

 regions than Kansas : C. iguanavus Cope, from New Jersey ; C. 

 propython Cope, from New Jersey ; and C. intermedins Leidy, from 

 the Rotten Limestone of Alabama. Only C. propython is well 

 known of these, and a comparison of the published figures and 

 descriptions by Cope (Extinct Batrachia, etc.) will convince one 

 of the very strong relationships with C. tortor, especially from 

 Kansas. Indeed, I half suspect that a careful comparison of 

 the specimens may reveal the identity of the species. A speci- 

 men discovered some time ago at Flagler, Colo., which I have 

 examined, probably from the Fort Pierre, may indicate another 

 species. 



Clidastes stenops. 



Edestosaurus stenops Cope, Proc. Amer. Phil. Soc, 1871, p. 330; Marsh, 



Amer. Journ. Sci., in, p. 264, June, 1872. 

 Clidastes stenops Cope, Cret. Vert., etc., pp. 133, 266, pi. xiv, ff. 4, 5; 



xvu, ff. 7, 8; xviii, ff. 1, 5; xxxvi, f. 3; xxxvm, f. 3. 



This species is very peculiar in lacking the expansion of 

 the prefrontal over the orbit anteriorly, its shape being more 

 nearly as it is in Platecarpus. In all other respects, however, it 

 is true Clidastes. "The prefrontal is of peculiar form, and dis- 

 plays the greatest difference from that of C. tortor. Instead of 

 being a horizontal bone, it is so oblique as to be nearly vertical. 

 From this follows an alteration of the relation of all the parts. 

 The squamosal suture with the frontal, which is marked by 

 peculiar concentric rugosities in both species of this genus, in- 

 stead of being on the upper, is nearly on the under surface, 

 though oblique to both. The lateral margin is subinferior and 

 plicate ; the crest of the inner side bounding the maxillary pro- 

 jects far below it in front. The characters are similar to those 

 of C. tortor ; but all the bones are more massive, though of the 

 same dimensions." 



Nothing is known of the extremities. 



