11 



beds, already mentioned as bounding a north and south valley. This 

 and the superjacent strata, which we pass over in going south, appear to 

 be conformable to those of the Bitter Creek series beneath them. ' I say 

 " appear," for slight differences of dip are not readily measured by the 

 eye ; yet I s.usi)ect that the conformability is very close, if not exact, 

 and similar to that mentioned by Meek and Bannister as exhibited by 

 the beds of the Washakie group, which lie upon the coal series east of 

 Creston. The white bluffs add perhaps one hundred feet to the eleva- 

 tion. On their summit is a thin bed of buff clay and sand rock, similar 

 to the upper strata of the Bitter Creek series, and containing numerous 

 shells, and some scattered teeth and scales of fishes. I called Mr. 

 Meek's attention to the 8i)ecimens of these shells, which I sent him, and 

 his reply was that most were of identical species with those of the coal 

 series, cretaceous, and that they presented no general peculiarity. 



At a short distance to the southward another line of white bluffs 

 extends across the line of travel. This is not more elevated than the 

 preceding one; I only. found remains of tortoises on it. Several miles 

 to the south we reach another bench, whose bluffy face rises four or 

 five hundred feet in buttress-like masses, interrupted at regular intervals 

 by narrow terraces. This line is distinguished for its brilliantly-colored 

 strata extending in horizontal bauds along the escarpment. They are 

 brilliant cherry-red, white, true purple with a bloom shade, yellow, and 

 pea- green , forming one of the most beautiful displays I ever beheld. The 

 lower portions are bright red, which color i3redominates toward the West 

 where the bluffs descend to a lower elevation. I found on them remains 

 of a turtle {Mmy enthnetus Cope,) and some borings of a worm in a hard 

 layer. On top of these are clay and slate rocks of a muddy yellow color 

 with their various ledges rising to perhaps two hundred feet. Continu- 

 ing now to the southeastward along the old stage-road, we cross South 

 Bitter Creek at the old Laclede Station. Some miles south and east of 

 this point we cross a band of buff" sand-stones, forming a bluff" of fifty or 

 more feet in elevation. Below it lie more white or ashen beds, which 

 contain remains of mammals and turtles rather decayed. A short dis- 

 tance beyond these, and forty miles from Black Butte Station, we reach 

 the base of the. enormous pile of sediment which I have called the 

 Mammoth Buttes. These form a horseshoe-shaped mass, the concavity 

 presenting south and eastwardly, the summit narrow, serrate and most 

 elevated to the east, and descending and widening toward the south. 

 I estimated the height of the eastern end to be at least one thousand 

 feet above the plain surrounding it. N^umerous mammalian remains* 

 demonstrated that this mass is a part of the Bridger Eocene, although 

 as Mr. Emmons, of King's survey, informs me, no continuous connection 

 with the principal area west of Green River can be traced. The total 

 thickness of the Green Eiver and Bridger formations on this section 

 cannot be far from twenty-five hundred feet at a very rough estimate. 



The point of transition from the Cretaceous to the Tertiary deposits, 

 as indicated by the vertebrate remains, is then in the interval between 

 the last plant-bed at the summit of the buff" mud rocks, and the mam- 

 mal bone deposit in the lowest of the ash-gray beds. Below this line 

 the formation must be accounted as Cretaceous, on account of the pres- 

 ence of the Dinosaurian Agatliaumas sylvestris; and those above it, as I 



* See The Monster of Mammotli Buttes, Penn Monthly Magazine, 1873, August. 

 *0n BatlimodoH, an extinct genus of Ungulates, Feb. 16, 1872. Hayden's Annual 

 Report, 1870, p. 431 ; Annual Eeport, 1872, p. 645. 



