GEOLOGICAL EEPOET. 289 



A piece of a fossil leg-bone, about one inch in diameter, which must, therefore, have 

 belonged to an animal of considerable size, was found by a member of the party at 

 the foot of a bluff far south of the road, at the base of the Uintah Mountains. From 

 its green color it is evident that it comes from No. 1, or the beds of transition to No. 

 2. I was, at the time, unluckily absent on a reconnaissance with Captain Simpson, 

 and was thus prevented from following up this trace, which might have led to the dis- 

 covery of another of those vast burial-grounds of pre-Adamitic mammalian life, winch 

 have made the names of Montmartre and Nebraska famous throughout the scientific 

 world. 



On a head branch of Henry's Fork, just beyond the southeast corner of the 

 military reservation of Fort Bridger, some 20 miles from that post, a limestone occurs 

 with a perfectly even conchoidal fracture, and of whitish color, with siliceous secre- 

 tions, and full of finely preserved Planorbis. Although I have not examined that 

 locality, I have no doubt that it is on a parallel with No. 2 of the above section. 



Along the road No. 2 forms the lower part of the hills near Fort Bridger. As the 

 strata rise toward southwest, it soon attains the height of the plateau over which the 

 road leads westward. It caps the breaks of Muddy Creek, on Captain Simpson's 

 new road to the Salt Lake Valley, as well as on the old road by Echo Canon. On 

 the latter it was found a few miles farther on near the crest of high hills, and some 

 strata at the top of the dividing ridge between Yellow Creek and Echo Creek seem to 

 belong to that series. 



No. 3 is best exposed in the more elevated western portion of the district. It 

 forms the lower part of the bluffs along Muddy Creek ; on the new road, it caps the 

 dividing ridge toward Sulphur Creek, is then interrupted by older upheaved strata, 

 but was found again on the western bank of Bear River, and on the top and on both 

 sides of the dividing ridge toward White Clay Creek. On the old road it also forms 

 the divide toward Bear River, at the Quaking- Aspen ridge, is then interrupted by 

 tilted older formations, extends again from Bear River to the Needles, near Yellow 

 Creek, and beyond forms part of the divide toward Echo Creek, and may extend some 

 distance down that creek. On the western branch of Bear River these strata are 

 found far up and down the stream, extending at least to the mouth of Yellow Creek. 



All the fossils in our collection from these rocks are fresh-water forms. In my pre- 

 liminary report, made at Camp Floyd in December, 1858, 1 had spoken of the Tertiary 

 formation of Green River as marine. I had done this, before the fossils had been 

 examined, upon the statement of Professor Hall, in Captain Stansbury's report, "that 

 from the South Pass to Fort Bridger the collections are all of marine Tertiary age," 

 which, if taken in connection with the remark of Captain Stansbury himself, that on 

 Ham's Fork very perfect shells were collected, can scarcely be referred to any other 

 formation than that in question. Moreover, some fossils which the same author had 

 figured in Colonel Fremont's report, and described as probably marine shells, closely 

 resemble some of this series, although we now think that they rather represent the 

 estuary deposits described below. 



The examination of the fossil remains has not furnished proofs from which f- 



decide upon the subdivision of the Tertiary period to which those strata belong ; but 

 37 bu 



