336 GEOLOGICAL SURVEY OF THE TEEEITOEIES. 



present saurian. We may therefore suppose that the latter exceeded 

 the former in dimensions. Should the humerus have been related to 

 the fore limb, as in Plesiosaurus doUchodirus, Conyb., the latter would 

 have had a length of 4 feet 3 inches; as the proportions of the radias 

 and phalanges are shorter, the limb was probably relatively shorter. 

 If related to the total length, as in the same Plesiosaurus, the humerus 

 would indicate a length of 17^- feet. As the cervical vertebrae become 

 attenuated, as compared with the dorsals to a greater degree in Polyco- 

 tylus than in Plesiosaurus, I have little doubt that the length of this 

 species exceeded that amount. 



William B. Webb, of Topeka, discovered the specimens from which 

 this species was first described, and liberally forwarded them to me for 

 examination and description. Other specimens have been discovered 

 since that time by various other persons. I have received numerous 

 fragments of an individual of about the size of the one above described, 

 which were found by Professor B. F. Mudge, at a point near the mouth 

 of the north branch of the Smoky Hill Eiver. 



ELASMOSAUEUS, Cope. 



Leconte's Notes on Geology of the Route of the Union Pacific Railroad, 1868, p. 68 ; 

 Cope, Proc. Acad. Nat. Sci., 1868, p. 92 ; Trans. Amer. Philos. Soc, 1869, p. 44. 



* This genus has been more completely preserved to us than any other 

 American representative of the order, and hence may be accepted as 

 most clearly expressive of its characters. In the interpretation of these, 

 however, considerable difficulty has been experienced, as the structure 

 forai api>ears, at first sight, to reverse to a remarkable degree the usual 

 X)roportions of known reptiles. No i)ortions of limbs were, however, 

 found with the vertebrae. The skeleton so nearly complete would. indi- 

 cate no violent disturbance of the carcass ,• but if there were, it would 

 be an unusual accident that all of the four limbs should have been re- 

 moved from their sockets without leaving even fragments. 



This genus is well distinguished from Plesiosaurus by the peculiarity 

 of the scapular arch. The mesosternum appears to be co-ossified with 

 the claviculi, and the three elements form a broad breast plate. If the 

 claviculus was ever united with the scapula, as in Plesiosaurus, no evi- 

 dence of it can be seen in the specimen. Both the clavicular and meso- 

 sternal elements are broader and more extended anteriorly. 



Elasimosaurus platyurus, Cope, (Leconte's Notes, loc. eit. Proc. 

 Acad. Nat. Sci., 1868, loc. cit, 92.) J)iscosaurus carinatus. Cope, (Le- 

 conte's Notes, loo. cit.) — This, after Mosasaurus, the most elongate of the 

 sea-saurians yet discovered, is represented by a more than usually com- 

 plete skeleton in the museum of the Academy of Natural Sciences in 

 Philadelphia. It was found by Dr. Theophilus H. Turner, the physician of 

 the garrison at Fort Wallace, a point situated near the boundary-line 

 separating Kansas from Colorado, a few miles north from the Smoky 

 Hill Fork of the Kansas Eiver. Portions of two vertebrae, presented by 

 him to Dr. Leconte when on his geological tour in the interest of the 

 United States Pacific Eailroad Company, were brought by the latter 

 gentleman to the academy, and indicated to the writer the existence of 

 an unknown plesiosauroid reptile. Subsequent correspondence with 

 Dr. Turner resulted in his employing a number of men, who engaged in 

 excavations, and succeeded in obtaining a large part of the monster. 

 Its vertebrae, one hundred and twelve in number, were found to be 

 almost continuous, except a vacancy of some four feet in the anterior 

 dorsal region. They formed a curved line, a considerable part of whose 



