JVb.2.] PEALE ON THE LARAMIE GROUP. 197 



and subsequent to tlie folding of the Laramie Group, as here exposed, 

 there must have been a period of erosion. I will refer to this again. 



Smithes ForJc and Bear River Region.— Along the east side of Bear 

 Eiver, between the valley and the bounding mountains, is a compara- 

 tively low area filled with gray and greenish-gray sandstones, which 

 sometimes form low hogbacks. These rocks are folded conformably with 

 the underlying older beds, and extend northward along Smith's Fork and 

 Salt Elver into the region of Snake Eiver, where they are beyond the 

 limits of our district. 



On Twin Creek, a branch of Bear Eiver, joining it from the east, these 

 sandstones are seen dipping to the westward 40 or 45°, and contain coal- 

 beds, in connection with which the following fossils were found : 



CorhicuJa ( Yeloritina) durl-ei. 

 Rhytopliorus meeMi. 

 Goniobasis elirysaloidea. 

 Goniohasis chrysaJlis. 

 Volsella {BracJiydontes) sp."? 

 Pyrgulifera Jmmerosa. 

 Memhranipora f 

 Ostrea sp.? 

 Neritina sp.? 



Besting on the beds containing these fossils were the red Conglomer- 

 ates of the Wahsatch Group, dipping to the eastward about 5°. This is 

 about the same unconformability noted on the west side of the Green 

 Eiver Basin. 



On Smith's Fork of Bear Eiver, three miles above its mouth, and 

 about twenty miles north of the Twin Creek locality, coal-beds again 

 occur in gray sandstones and contain Unio vetustus and other obscure 

 Laramie forms. Twenty miles farther north is another fossil locality, 

 from which the following were obtained : 



Corhicula (Yeloritina) durlei, 

 CorhiiJa pyriformis. 

 Goniohasis elirysaloidea. 

 Goniohasis cleburni. 

 Pyrgulifera liumerosa. 

 Unio vetustus. 

 Ostrea sp.? 



The more northern extension of these beds was not carefully traced, 

 but it was evident that they form a large part of the siu-face between 

 Salt Eiver Yalley and the Blackfoot region south of Snake Eiver. 



GENERAIi REMARKS. 



The bottom of the Laramie Sea appears to have been subjected to a 

 constant and gradual subsidence, as the character of the strata indicates 



