366 GEOLOGICAL SUEVEY OF THE TEEEITOEIES. 



EEPTILES. 



CEOCODILIA. 

 OE-OCODILUS. 



When an isolated vertebra of a crocodile, from tlie Tertiary formation 

 of Wyoming, was submitted to my inspection in 1868, it did not lead 

 me to anticipate thje many crocodilian remains which have since been 

 discovered in the same Territory. No trace of crocodiles had previously 

 been detected in the extensive Tertiary deposits of Dakota aud Ne- 

 braska, which have yielded such a multitude of remains of mammals and 

 turtles. 



Crocodilus aptus. 



A species named from a single vertebra, found by Col. John A. 

 Knight, U. S. A., near South Bitter Creek, Wyoming. The animal was 

 about the size of the Mississippi Alligator. 



Crocodilus Mliotti. 



A species assumed to be different from the former, and chiefly indi- 

 cated by the greater part of a skull, broken into fragments, found on 

 oue of the tributaries of Green Eiver, Wyoming, during Prof. Hay- 

 den's exploration of 1870. The skull is about a foot and a half in length, 

 and has nearly the shape of that of the existing Crocodile of the Nile. 



Many additional remains of crocodiles obtained by Drs. Carter and 

 Corson, in the vicinity of Fort Bridger, Wyoming, have been sent to 

 me. Among these there is a nearly complete lower jaw, which was dis- 

 covered by Dr. Corson, imbedded in a green sandstone. I am uncertain 

 whether it pertained to the species just indicated. 



Prof. Marsh has collected a number of remains at Grizzly Buttes 

 and other localities in the neighborhood of Fort Bridger, which he at- 

 tributes to four species distinct from those above named. They are 

 noticed in the American Journal of Science and Arts for 1871, under 

 the names which follow : 



Crocodilus zipJiodon. 



A comparatively small animal in its family, and judging from the 

 characters af the teeth not a true crocodile. 



Crocodilus liodon. 



Crocodilus affinis. Crocodilus Grinnelli. 



CHELONIA. 



Testudo. 



Testudo Corsoni. 



Dr. Joseph K. Corson, U. S. A., stationed at Fort Bridger, in the 

 intervals of his professional duties, directs his attention to the inves- 

 tigation of the natural resources of the country. One of the results 

 of his explorations is the discovery of many interesting fossils of the 

 Bridger Tertiary formation, specimens of which we have had frequent 

 occasion to mention. Among the fossils found by him last summer, 

 and presented to the Academy of Natural Sciences of Philadelphia, is 

 the fore part of a plastron of a huge land-turtle, equal to the largest 



