UPPEE BEAR KIVEE VALLEY. 329 



tremely local development, and which, from their position in the angle of 

 the two high ranges of the Wahsatch and Uinta, have evidently been formed 

 in an estuary at the mouth of some fresh- water stream, whose waters have 

 spread them out conformably, for a considerable distance, over marine beds. 

 Smaller outcrops of these estuary beds are visible at various points along 

 the railroad, in fresh cuts, between Bear River City and Evanston. 



To the south of Bear River City, in the shallow bottom of one of the 

 tributaries of Sulphur Creek, is a spring of petroleum, near which a well 

 was sunk for obtaining oil, with about the same result as at Judge Carter's 

 oil-wells, already mentioned in Chapter II. It comes evidently from the 

 Colorado beds, and probably from the same horizon as in the valley of the 

 Little Muddy. 



To the north, the upturned Cretaceous beds pass beneath the horizontal 

 strata of the Vermillion Creek series, which form the main mass of the Aspen 

 Plateau. These consist generally, as has already been seen, of alternations 

 of coarse gray sandstones and reddish and cream-colored arenaceous clays 

 and marls, giving to the blujff exposures a general striped appearance. The 

 correctness of the conclusion, arrived at on broad grounds of corresponding 

 lithological character and stratigraphical relations, that these Tertiary beds 

 belong to the lowest series observed, and correspond to the Vermillion Creek 

 group of the Green Eiver Basin, has, since the completion of the field-work 

 of this Survey, received confirmation by the recent discovery by Professor 

 Marsh's assistants of an interesting series of vertebrate remains in the hills 

 to the east of Evanston, which indicate the lower beds of the Eocene Ter- 

 tiary. The most important forms recognized from this collection are those 

 of the genus Coryphodon, an ungulate mammal characteristic of the London 

 clay, and the lower portion of the argile plastique of the English and French 

 geologists. The following are some of the most characteristic forms: 



Coryphodon lamatus. 

 Corypliodon radians. 

 Coryphodon semicinctus. 

 JEoJiippus pernix. 



As no beds, which could be distinctly identified as corresponding to the 

 Bridger series, were found to the east of the line of Aspen Plateau, this line 



