252 KANSAS UNIVERSITY SCIENCE BULLETIN. 



the alisphenoid, and so the bone is named by Parker. (Trans. 

 Roy. Soc, 1879, p. 615.) But there is another element, the 

 epipterygoid, posterior to it, and immediately anterior to the 

 petrosal, which has been supposed to be the true alisphenoid. 1 

 Leaving this question, and adopting for the bone in question the 

 provisional name of postoptic, I remark that it is typically 

 triradiate, sending two branches up and one downward," etc. 2 



In one or two instances I have seen a slender rod of bone in 

 Clidastes, which I have thought to be the epipterygoid, but I 

 have never been sure. Marsh 3 described the epipterygoid as a 

 rod of bone in Platecarpus, and Osborn also identified it as a 

 flattened rod in Tylosaurus. It is strange, however, that it does 

 not appear more frequently in the many skulls of these animals 

 discovered in the Kansas Cretaceous. 



Lying by the side of an excellent skull of Clidastes tortor in 

 the museum there is a slender rod, with a sharply truncated 

 extremity, whose position in the skeleton I do not know, unless 

 it belongs in the hyoidean apparatus. It is too large and too 

 long to be an epipterygoid. The bone is cylindrical, gradually 

 tapering, with the truncated surface oval. 



Platecarpus Species from North Dakota. 



In plate XIII is shown an ischium and some paddle bones of 

 a species of Platecarpus, recently sent me for examination by 

 Professor Sardeson of the University of Minnesota. The bones 

 were obtained from near Milton, in the northeastern part of 

 North Dakota, enclosed in a blue shale very much like that of 

 western Kansas. Associated with the specimen were others of 

 Hesperornis, etc., all evidently belonging to the upper part of 

 the Niobrara Cretaceous. The present specimen differs from 

 any species of Platecarpus that I know, in the shape of certain 

 bones, and indicates a distinct species. But I do not know all 

 the species that have been described from the Kansas Cretaceous 

 in this genus, and will leave its determination until further in- 

 formation is forthcoming. 



The following notes were made by me after an examination 

 of the type specimens at the Yale museum, two years ago; I 



1. This is, however, contested by Baur, because of the presence of both the alisphenoid and 

 epipterygoid in Uphenodon. 



2. Cope, An. Rep. U. S. Nat. Mus. for 189S, p. 187. 



3. Marsh, Amer. Journ. Sci. 



