46 Cincinnati Society of Natural History. 
There seems to be no unconformability of the beds included in this 
Group, and the different beds pass from one to the other gradually ; 
but to the leaden-gray, somber, indurated, arenaceous clays, which 
cover a large area east of Fort Bridger, and weather into such unique 
architectural forms, and contain a large variety of vertebrate remains, 
Dr. Hayden gave the provisional name of the “Bridger Group.” The 
calcareous layers which underlie the Bridger Group, and are so well 
displayed lower down on Henry’s Fork, he referred to the “ Green river 
Group.” Intercalated with the clays of the Bridger Group are beds of 
rusty-brown and gray sandstones, all tending to a concretionary struc- 
ture, and disintegrating by exfoliation in thin concentric layers. 
Sometimes there are beds of sandstone which form an aggregate of 
concretions, In the whole mass, arenaceous materials predominate. 
As we descend, the calcareous sediments prevail, until chalky lime- 
stones and marl are greatly in excess. 
The Green River Group is seen to the best advantage along the 
valley of Green river, where the sides of the bluff blanks rise to a per- 
pendicular height of 500 feet or more. Ten miles east of Green river 
Station, the Green River Group disappears abruptly on the south side 
of Bitter creek, and the coal formations come up to view. On the north 
side, the eastern limit of the Green River Group is most sharply marked 
by a long, high, white bluff, that extends off, far to the northeast 
toward the South Pass. | j 
The dip varies from 3° to 5°, and the laminated calcareous shales 
gradually pass down into yellow, gray, and brown indurated arenaceous 
clays, sands, and sandstones, until the well-defined coal strata are ex- 
posed, without the least appearance of discordancy. | 
In traveling from Bear river to Great Salt Lake valley, soon after 
leaving Carter station, toward the west, pinkish Tertiary beds are ob- 
served. They seem to rise from beneath the Bridger Group. Their 
dip is about northeast 3° to 5°, and they have evidently been disturbed 
slightly by the later movements which elevated the Uinta range. They 
are composed of red, indurated, arenaceous clays, with beds of grayish 
and reddish-gray sandstones alternating; and for this series of strata 
Dr. Hayden proposed the name of the “ Wasatch Group,”’ Pinkish and 
purplish clays are the dominant features, and give the lithological 
character of the group as far west as Echo canon, when the conglom- 
erates prevail. The latter is full of beds of sandstone, largely concretion- 
ary, but the sandstones or harder layers are seldom of a reddish color. 
[To BE ConrINUED. | 
