1 88 The Tertiary Formations of the [March, 



eastern end of the Uinta Mountain range is another Tertiary- 

 group that has received the name of " Uinta group " from Mr. 

 King, and " Brown's Park group " from Major Powell. It is pos- 

 sible that this group was deposited continuously, at least in part, 

 with the Bridger group, but at the places where the junction be- 

 tween the two groups has been seen in this region, there is an 

 evident unconformity, both of displacement and erosion. 



" The group consists of fine and coarse sandstones, with fre- 

 quent layers of gravel, and occasionally both cherty and calcare- 

 ous layers occur. The sandstones are sometimes firm and regu- 

 larly bedded, and sometimes soft and partaking of the character 

 of bad-land material. The color varies from gray to dull reddish- 

 brown, the former prevailing north of the Uinta mountains and 

 the latter south of them. 



" The only invertebrate fossils that are known to have been dis- 

 covered in the strata of this group are some specimens of a Physa, 

 very like a recent species. Therefore, invertebrate palaeontology 

 has furnished no evidence of its assumed Tertiary age and lacus- 

 trine conditions of its deposition. Its fresh -water origin, however, 

 seems unquestionable, because of its intra-continental position, its 

 limited extent, and the fact that none but fresh-water deposits are 

 known in this part of the continent that are of later date than the 

 close of the Laramie period." 



To these remarks of Dr. White I add, that several species of 

 Vertebrata have been obtained from this formation by Professor 

 Marsh, who has determined from it a few genera of Tertiary and 

 Upper Eocene character. Such are, of Mesodonta, the genus Hyop- 

 sodus and of Ungulata, the Perissodactyle form Amynodon. 



THE WHITE RIVER. 



The material of which the beds of this formation are composed 

 in their eastern division, are calcareous clays and marls, alter- 

 nating with a few unimportant strata of light-colored sandstone. 

 They are white and gray, with occasionally a pink and red, and 

 sometimes greenish tinges. The beds of the western deposit in 

 Oregon, consist of a more or less indurated mud, which is, 

 according to King, of trachytic origin, which is rarely hard, and 

 frequently rather soft. Its predominating color is light green, 

 but is frequently olive and light brown. The depth of the formation 

 on the White river of Nebraska is, according to Hayden, 1 about 1 50 

 feet; and on Crow creek, Colorado according to King, 2 300 feet. 

 Sixty miles east of Crow creek I estimate its thickness as some- 

 P . 153. 



