PEALE.] GEOLOGICAL FOEMATIONS— POST-CEETACEOUS. 181 



Bed No. 3, and a portion of No. 2, I have called the Lower Dakota, 

 the name suggested by Mr. Holmes. (Report 1875, p. 261; see also p. 

 88 of same report.) 



Above the Colorado shales, in the Book Olifts, is a bed of sandstone 

 that forms a well marked escarpment. This bed probably represents the 

 base of the Fox Hills group. Above it are shales and sandstones as 



follows : 



Feet. 



1. Sandstones and shales 650 



2. Massive sandstones, with a few bands of shaly sandstones ..... 600 



I am inclined to consider a part, if not the whole, of layer No. 2 as 

 belonging to the Laramie group ; but, as already stated, the line between 

 the two formations cannot be definitely drawn in the absence of fossils. 



In the Little Book Cliffs the sandstones and shales referable to the 

 Fox Hills group are about 1,000 feet in thickness. (See section p. 177, 

 Chap. TIL) 



Professor White had good exposures of the Fox Hills group farther 

 north, and to his reports the reader is referred for details, especially 

 those of a paleontological nature. At no point in the district did I ob- 

 tain any fossils from its strata. 



POST- CEETACEOUS. 



Dr. Hayden first pointed out the transitional character of the sand- 

 stones that lie between the marine beds of the Cretaceous and the fresh- 

 water beds of the Tertiary.* The paleontological evidence has been 

 conflicting, those studying the fossil flora differing from vertebrate 

 I)aleontologists. As Dr. White has ably shown in his comparison of the 

 Cenozoic and Mesozoic groups, the testimony of invertebrate paleon- 

 tology but confirms the position of Dr. Hay den. t For these transitional 

 beds Dr. White has proposed the name Post Cretaceous. The beds of 

 the Laramie group are the ones so designated. They consist mainly of 

 sandstones. 



In Area A no beds of Post Cretaceous age were noted ; so I pass to 



Area B. — In the western part of this district there is no distinct litho- 

 logical line separating the Laramie group from the Fox Hills below 

 nor from the Wahsatch beds above. In passing up through the sand- 

 stones, it is noticed that they have a tendency to separate into massive 

 bands, between which reddish shales or laminated sandstones appear. 

 As we ascend still higher, they pass insensibly into the shales of the 

 Green River Group. 



On Grand River, near the mouth of Roan Creek, there are bluffs in 

 which about 500 feet- of sandstones outcrop. These sandstones are 

 probably the upper part of the Laramie group, the variegated beds jusfc 

 above representing the Wahsatch group. 



In the Grand Hogback Range, just east of Cactus Valley, the follow- 

 ing fossil plants were obtained, the identification being by Professor 

 Lesquereux : 



Ficus auriculata^ Lesqx. 



Ficus planieostata, Lesqx. 



Ficus planicostata var. Goldiana^'hesqx. 



Diospiros crassinervis, Lesqx. 



Salix ? 



Cinnamomum, fragment. 



* Eeport U. S. Geol. Survey, 1870, pp. 165-166. 

 t Bulletin No. 3, vol. iii, pp. 6^4-629. 



