WILLISTON AND CASE: KANSAS MOSASAURS. 29 



men. A stronger reason for doubt is the statement that the consoli- 

 dated vertebrae belong to the posterior "lumbar" region, and that 

 the last vertebrae had small tubercles indicative of chevrons. In the 

 reptiles which we have examined, the chevrons do not begin immediately 

 behind the pelvis, but are separated by a longer or shorter region in 

 which the vertebrae bear elongated diapophyses alone. If the 

 conjoined vertebrae figured by DoUo are in reality sacral, it would 

 appear that the animal is an exception to Clidastcs and such lizards as 

 we have examined. Furthermore, the pelvis must have been of a 

 different structure from that in the Kansas genera of the Pythonomor- 

 pha, for, in these, it is evident that the ilium had an oblique position, 

 and could have been attached to but a single diapophysis. 



CLiDASTES WESTII, N. SP. 



A specimen of much interest in the University collection differs so 

 markedly from the other forms represented by specimens, as also from 

 the descriptions of the known species, that we are constrained to 

 regard it as new. It was collected by Mr. C. H. Sternberg from the 

 uppermost of the Niobrara beds, in the vicinity of the old town of 

 Sheridan. The character of the associated invertebrate fossils seems 

 to indicate a different geological horizon, either the Fox Hills group, 

 or transition beds to that group. The specimen consists of a complete 

 lower jaw, quadrate, portions of the skull, the larger part of the verte- 

 bral column, and the incomplete hind and fore paddles. The 

 vertebrae preserved are in two series, the one, numbering thirty-three, 

 continuous with the skull; the other, sixty-three in number, all chev- 

 ron caudals. The terminal caudals preserved indicate that there were 

 several more in life, perhaps five or ten ; the first of the series was 

 evidently among the first of those which bore chevrons. Altogether 

 the tail may have had seventy-five chevron caudals. The lengths of 

 the two series are respectively seventy-one and seventy-two inches. 

 Assuming that there was the same number of precaudal vertebrae as 

 in C. 7'elox, the entire vertebral column would have measured in life 

 fifteen feet and four inches. The lower jaw shows the skull to have 

 been very nearly twenty-four inches in length, making, for the animal 

 when alive, a length of seventeen and one-half feet. This is one of 

 the largest species, and it is interesting to observe that the real 

 size here, as usually elsewhere among fossil vertebrates, is less than 

 supposed. It is doubtful whether there is a Cliifasfrs known that 

 exceeded twenty feet in length. 



While the skeleton was only about one half longer than the speci- 

 men of C. 7'c/ox described in the foregoing pages, or of about the 



