436 GEOLOGICAL SURVEY OF THE TERRITOEIES, 



bed of coal just above it soon follows ; then a bed of shells containing 

 oysters, more and less numerous at different points, may be traced for 

 some distance before it also disappears. JSear the latter point, a bed of 

 melanian and other fresh-water shells is seen a few feet above them. 



A section, carried for eight miles south of Black Butte station, exhib- 

 its the relation of the Bitter Creek series to the superincumbent Tertia- 

 ries very instructively. The whole series rises slightly to the southward, 

 and more distinctly to the westward, so as to form an escarpment as the 

 eastern border of an open valley, which extends south from the railroad 

 iust west of the station. The heavy bed of sand-rock is here as else- 

 where the landmark and stratigraphical base-line. Moving south from 

 the railroad, we keep along the strike of the lower coal-beds. Just 

 above the sandstone bed the softer stratum thickens, and six miles from 

 the station is covered with the debris of immense numbers of LeptestJies 

 crassatelUformis. Passing over the edges of the strata toward the south- 

 east, I counted eight beds of coal, separated by various short intervals, 

 the eighth being the heaviest, and five or six feet thick. Above this one, 

 three thin beds of lignite were crossed in succession, each accompanied 

 with an abundance of leaves of chiefly dicotyledonous plants. Then 

 came the ninth bed of coal, and then in order three more beds of lignite, 

 with abundant leaves. During this time the ascent became less steep, 

 and a number of level tracts were passed before reaching the upper bed 

 of lignite. Beyond this I passed another short flat, which was marked 

 by a number of worn banks of the light ash-color that distinguishes the 

 material of the bluffs of the Green River Tertiary which overlie the coal- 

 series near Rock Springs. I had not ridden a quarter of a mile before 

 reaching a low line from which one of my men picked up a jaw of a 

 small mammalian allied to the Bridger Hyopsodus, or Hyracotherium of 

 the Eocene of France and Switzerland, and a number of Paludina-\\)^Q 

 shells. I had thus reached the summit of the Bitter Creek formation, 

 which did not appear to be much more than three hundred and fifty feet 

 above its base at the railroad. In full view, a mile or two to the south, 

 rose the first of the benches which constitute the levels of the Green 

 River formation. Between this and the first mammal-producing bed 

 rose three banks, one beyond the other, measuring altogether one hun.- 

 dred and twenty feet; perhaps the lowest was ten feet above the first 

 bank, and this one not more elevated above the last lignite and leaf bed. 

 In all of these, I found bones of Green River Vertebrata exceedingly 

 abundant, but all dislocated and scattered, so as to be rarely in, juxta- 

 position. These consisted of the following species : 



Fishes: 



Glastes (?) glaber. 



Reptiles : 



Emys megaulax. 



Emys pachylomus. 



Emys euthnetus. 



Trionyx scutumantiquum. 



Alligeiior Jieterodon. 

 Mammals : 



Orotherium vasacciense, and fragments of others too imperfect for 

 determination. 



In the third bank, in immediate juxtaposition with the remains just 

 enumerated, I found another thin bed of lignite, but this time without 

 any visible leaves. In a fourth line of low bluffs, a little beyond, I found 



