248 KANSAS UNIVERSITY SCIENCE BULLETIN. 



dispelled this doubt, but has strengthened my opinion of its in- 

 validity. There is less difference, I believe, between Holosaurus 

 abruptus and Platecarpus coryphaus than between Clidastes relox 

 and C. dispar, and especially between the latter and C. stenops, 

 mentioned below, forms presenting similar differences to the 

 chief one separating Holosaurus from Platecarpus. 



Holosaurus has no z} T gosphenes, as I at one time suspected it 

 possessed, nor can I distinguish any difference in the skull as it 

 lies in the matrix with the dorsal surface concealed. It is to be 

 hoped that the specimen may be removed from its matrix at no 

 distant day, and so preserved that all parts may be available 

 for comparison. 



There are, however, certain differences in the girdles and 

 limb bones which distinctly remove this species from those of 

 Platecarpus hitherto made known. Plate XLI, figs. 2 and 2a, 

 of my report upon the Kansas mosasaurs, show the distinctive 

 forms of the pubis and ischium, easily distinguishable from 

 those bones of Platecarpus coryphseus. The specimens there 

 figured I found isolated near Monument Rock, and I was never 

 sure where they belonged, though, from their general resem- 

 blance to the bones of Platecarpus, I referred them to that genus. 

 These differences are seen in the greater expansion of the distal 

 extremity of the ischium, and in the shape of the proximal end 

 of the pubis. The radius figured in plate LVII, figs. 1 and 2, 

 also belongs with this species, distinguishable by the differences 

 in form from that of Platecarpus coryphtrus. I know of no other 

 bones which may be confidently referred to that species, nor 

 are the differences in other bones at all conspicuous or even 

 perceptible. There is, of course, a possibility that the species 

 H. abruptus may prove to be identical with some species of 

 Platecarpus described by Cope. Evidence of such identity can 

 only be ascertained by a study of the types. 



Clidastes stenops Cope. 



At the time of the publication of my report upon the mosa- 

 saurs of Kansas, I had never recognized a specimen of this 

 species, of which nothing has been published since its original 

 meager description by Cope. Recently a considerable part of a 

 skeleton, which I refer to this species, has been obtained from 

 Mr. Chas. Sternberg, who collected it in western Kansas. The 



