400 GEOLOGICAL SURVEY OF THE TERRITORIES. 



present an unusual accident. The neural spines of the dorsal region are 

 so elevated and closely placed as to allow of little or no vertical motion 

 of the column downwards, while those of the cervical and caudal region 

 being narrower, the elevation of the head is quite possible, and an 

 upward flexure easy. 



The habit of this species, like that of its nearest known allies, was 

 raptorial, as evinced by the numerous canine-like teeth, and the fish 

 remains taken from beneath its vertebrae. 



The general form of this reptile, whether it was furnished with large 

 posterior limbs or not, was that of a serpent with a relatively shorter, 

 more robust, and more posteriorly placed body than is characteristic of 

 true serpents, and with two pairs of limbs or paddles. It progressed 

 by the strokes of its paddles, assisted by its powerful and oar-like tail. 

 The body was steadied by the elevated keel of the median dorsal line, 

 formed by the broad, high neural spines. The snake-like neck was 

 raised high in the air, or depressed at the will of the animal, now arched 

 swan-like preparatory to a plunge after a fish, now stretched in repose 

 on the water or deflexed in exploring the depths below. 



Differences from other Sauropterygia. — The only genus with which it is 

 necessary to compare this present one is Gimoliasaurus. The following 

 may be noted as generic distinctions : The series of cervicals rapidly 

 diminishes in Gimoliasaurus in absolute size and in relative length of 

 the vertebrae, which are not compressed. In the present gen us. they 

 maintain a similar and increased length for a considerable distance, 

 diminish in length very gradually and are much compressed. The 

 diapophyses of the dorsal vertebrae, as they descend, in Gimoliasaurus, 

 continue well developed until they attain the inferior planes of the 

 centrum, and have there a downward direction. In Elasmosaurus they 

 cease while yet on the middle of the centrum and are replaced by pits 

 throughout the remainder of the length. 



The neural canal is everywhere markedly larger in Gimoliasaurus. 



As the characters of lesser significance may be added, that in Gimo- 

 liasaurus magnus the dorsals with elevated diapophyses are considerably 

 larger in the centra than those in which they are situated lower down. 

 In E. platyurus these vertebrae are of relatively equal length. 



The cervical pleurapophyses in G. magnus are anteriorly considerably 

 stouter and less flattened ; the same applies to more anterior vertebrae, 

 where they are flatter in both. 



In comparing this species with the Gimoliasaurus grdndis, Leicly, from 

 Arkansas, we observe, first, the generic character of the strong inferior 

 diapophyses in the latter. That species marks itself also as a preemi- 

 nently short-necked form, as these anterior dorsals are even shorter than 

 in C. magmis, being nearly twice as wide as long. The depth of the 

 articular faces is also relatively greater than in the E. platyurus. 



Localities. — This species has been found in various parts of Kansas 

 besides that whence the specimen above described was procured. Pro- 

 fessor B. F. Mudge obtained vertebrae from a point thirty miles east of 

 Fort Wallace, which probably belong to this animal. 



PYTHONOMORPHA.* 



This order is more extensively represented in the cretaceous beds of 

 Kansas than any other, no less than six species having been determined 

 up to this time. A seventh, Lioclon dyspelor, Cope, has been discovered 



*For tlie definition of tMs order see Trans. Amer. PMlosoph. Society, 1869, p. 175, and 

 Proc. Boston Soc.N. Hist., 1869, p. 253. 



