330 GEOLOGICAL SUEVEY OF THE TEKEITOEIES. 



The tibia is a narrow bone, expanded at both ends ; the fibula is like 

 that of Flesiosaurus, but wider, or partly discoid. It has been known 

 to naturalists, but not determined. Thus, I figured it for Liodon Icevis,* 

 and Leidy figured it for an Upper Mississippi species.t 



There was for a considerable time doubt as to the structure of the 

 anterior limbs in this order, some authors asserting their ambulatory, 

 others their natatory character. Dr. Leidy inferred that they were 

 flippers, after an examination of a humerus from Mississippi. This 

 turns out to belong to a turtle, {Protostega tuherosa, Gojie ;) hence the 

 first real determination of the character of these members was made by 

 the writer in his description of the four limbs of Clidastes pro])yt]ion, 

 the first species in which they were well represented by specimens. 



CLIDASTES, Cope. 

 Proc. Acad. Nat. Sci., Phila., 1868, p. 233; Trans. Amer. Philos. Soc, 1870, p. 211. 



Vertebrae with the zygosphen articulation. [Palatine bones flat and 

 alate ; the teeth not exposed at their bases unequally. This point has 

 not been observed in the type species C. iguanavus.] 



Clidastes cineeiaeum. Cope, (Proc. Amer. Philos.- Soc, 1870, 583.) — 

 Two individuals from different points near the Korth Fork of the Smoky 

 Hill Eiver, Kansas. 



The largest species of the genus. 



Clidastes vymanii, Marsh, (Amer. Jour. Sci. and Arts, June, 1871.) — 

 From two individuals from the Smoky Hill Eiver and its iforth Fork. 

 A small species. 



Clidastes pumilits. Marsh, (loc. cit.) — ^From one individual from the 

 Smoky Hill Eiver. The smallest known Mosasauroid, according to Pro- 

 fessor Marsh, reaching a length of only 12 feet. 



EDESTOSAUEUS, Marsh. 



Amer. Jour. Sci. and Arts, 1871, June. 



Vertebrse with the zygosphen articulation ; palatine bones narrow, 

 partly vertical ; the bases of the pterygoid teeth exposed on one side, or 

 pleurodont. (It is uncertain whether the type of Clidastes presents this 

 structure or not.) 



EDESTOSAUiiTJS TOETOE, Copc, (Proc. Amer. Philos. Soc, 1871, De- 

 cember.) — A slender species of some 30 feet in length, with a narrow, 

 pointed head of 2t} feet. Its teeth are compressed, and with a cutting- 

 edge fore and aft, and were 18 in number on the under jaw j the palate 

 was armed with 11 teeth. 



Found near Fossil Spring. 



EDESTOSAUEUS STENOPS, Cope, {loc. cit.) — A spccics not unlike the 

 last, founded on one individual of rather heavier proportions. Its 

 prominent character is the narrowness of the face in front of the orbits, 

 the prefrontal bones being nearly vertical instead of horizontal. 



From Fossil Spring. 



EDESTOSAUEUS DiSPAE, Marsh, (Amer. Jour. Sci. and Arts, June, 

 1871.)— Smoky Hill Eiver. 



EDESTOSAUEUS VELOX, Marsh, {loc. cit.) — Near the North Fork of the 

 Smoky Hill Eiver. 



* Trans. Amer. Philos. Soc, 1869, p. 205. 



t Cretaceous Keptiles U. S., Tab. VIII, Fig. 10. ' 



