o6G GEOLOGICAL SUETEY OF THE TEEBITOELES. 



EEPTILES. 

 CEOCODILIA. 

 CEOCGDILirS. 



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

 of TTvoming'. was submitted to my inspection in 1S68. it did not lead 

 me to anticipate the many crocodilian remains which have since been 

 discovered in the same Territory. Xo trace of crocodiles had previously 

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

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

 turtles. 



Crocodihis 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. 



Crocodihis EUiotti. 



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

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

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

 den's exi^loration 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 ]S^ile. 



Many additional remains of crocodiles obtained by Drs. Carter and 

 Corson, in rtie 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 : 

 « 



Crocodihis zipliodon. 



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

 characters of the teeth not a true crocodile. 



Crocodihis Uodon. 



Crocodihis affinis. Crocodihis Grinnelli, 



CHELO^'IA. 



Testi'do. 



Tesfudo Corsoni. 



Dr. Joseph K. Corson, U. S. A., stationed at Fort Bridget, iu 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 discovers* of many interesting fossils of the 

 Bridger Teitiary 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 largiest 



