10 



a bed of melaniaus and other fresli-water shells is seen a few feet above 

 them. 



A section, CEirried for eight miles south of Black Butte Station, exhib- 

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

 tiaries very instructively. The whole series rises slightly to the south- 

 ward, and more distinctly to the westward, so as to form an escarp- 

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

 the railroad, just west of the station. The heavy bed of sand-rock is 

 here as elsewhere the land mark 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 Le])testhes 

 crassatelliformis. 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 

 camethe 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 bluft's of the Green Eiver Tertiary which overlie the coal 

 series near Bock 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 Syopsodus or Hyracotherium of 

 the Eocene of France and Switzerland, and a number of Paludiua like 

 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 

 Eiver 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 Eiver vertabratse exceedingly 

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

 position. These consisted of the following species : 



Fishes, Clastes (f) glciber. 

 Eeptiles, Emys meganlax. 



Emys pachylonms. 



Emys entlioveius. 



Trionyx seutumantiquum. 



Alligator keteorodon. 



Mammals, Orotherimn vasacciense, and fragments of others too imper- 

 fect 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 bej^ond, I found 

 that remarkable mammal Metalophodon armatus, with its dentition nearly 

 complete, in connection with fragments of other mammals and reptiles. 



Behind these rises the first line of white bluffs, already described, 

 which extends away to the east ; to the west it soon terminate in a 

 high escarpment, in north and south line with that of the Bitter Creek 



