328 DESCEIPTIVE GEOLOGY. 



Kivfer near the mouth of Slater's Fork, described in Chapter I. They are 

 separated by an interval, bare of outcrops, from the sandstones west of Bear 

 River City, but correspond with them in strike, and stand nearly vertically, 

 having an inclination of 70° to 80° to the southeast. They have evidently 

 fallen over somewhat to the northwest, however, as the beds in the upper 

 portion of the ridge, which thin out remarkably in a very short distance, 

 have been completely bent over in that direction, so as to give the section 

 almost the appearance of an anticlinal fold. They are formed of sandstones, 

 marls, and clays, with a few bituminous and gypsiferous seams, and are 

 remarkable for the fine definition of their bedding-lines, the strata varying 

 from half an inch up to a foot or more in thickness. They abound in fossils 

 of prevailing fresh and brackish- water types, of which the following forms 

 have been described : 



Unio vetustus. 



Unio heUipUcatus. 



Corhula pyriformis. 



Corbula Engelmanni. 



Corhicula (Veloritina) DurJceei. 



Bhjtiphorus priscus. 



Pyrgulifera humerosa. 



Limncea nitidula. 



Campeloma macrospira. 



Campehma, undet. sp. • 



Viviparus Conradi. 



Ostrea f 



These beds, from their stratigraphical position, evidently belong to the 

 same conformable series as the Bear River City beds, being overlaid a short 

 distance to the north by horizontal strata of the Vermillion Creek Eocene, 

 and, on account of the number of fresh-water shells which they contain, 

 have been frequently quoted as proving the Tertiary age of the coal-bearing 

 rocks. Professor F. B. Meek's latest opinion, however, was, that the balance 

 of evidence offered by their fauna, which have all been submitted to his 

 determination, was in favor of a Cretaceous age. In any case, it would seem 

 hardly advisable to give much weight to the evidence of beds of such ex- 



