Douglass : A Geological Reconnalssance. 231 



This region is a miniature bad-land ; yet where the deposits are not 

 washed bare, especially on the northern faces and more gentle slopes, 

 there is a thick growth of trees, shrubs, grasses, and other vegetation. 

 The grass is thick and heavy at the alluvial bases of these hills. The 

 place appeared favorable for the discovery of vertebrate fossils, so it 

 was hoped that at least enough bones might be found to fix beyond 

 doubt the age of the deposits. The lower beds were so similar to 

 the Lower Oligocene in other places, that there seemed little doubt 

 that they belonged to the Titanotherium horizon, but we searched in 

 vain for fossils. In the cream-colored beds above, which weather into 

 cliifs or steep slopes, and contain many brown porous or cellular 

 nodules, we found bones and teeth of various animals such as 

 Eianys (a mouse), Ischyromys, Gymnoptychus, Palceolagus (an ancient 

 rabbit), Mesohippus (a small horse), Aceraiheriuvi (a rhinoceros), 

 Merycoidodon, Leptomeryx, etc., besides the shells of land turtles. 

 The fossils show plainly that these are the Middle White River, or 

 Oreodon beds. In the green sandy beds were many bones of the 

 rhinoceros Aceratherhim iridactylum. 



From the top of one of the smaller buttes, as from the top of White 

 Butte, one gets a good view of the surrounding country, and the fol- 

 lowing events in its geological history seem plainly carved on the 

 landscape, and recorded in the rocks beneath our feet : 



(i) At some time, after the deposition of the Fort Union beds, 

 there was an increase in the grade of the streams, which in later 

 Eocene times carved broad valleys in the strata. (2) In early Oli- 

 gocene tirnes by the partial obstruction of the drainage deposits were 

 made in these old Eocene valleys. Probably at times there were quite 

 large lakes and marshes. (3) There were many changes during the 

 Oligocene, and there were apparently several stages of deposition and 

 erosion. At several different intervals during the long period condi- 

 tions were favorable in some places for the preservation of the remains 

 of the turtles and mammals, which now lie at successive levels in the 

 beds of White Butte. The reasons for believing that the White River 

 (Oligocene) deposits were made in a river valley in the Eocene strata, 

 is the fact {a) that they are evidently, at least in part, deposits made 

 by streams, and in lakes and marshes, {b') Some of the strata appar- 

 ently lie at the same level as Early Tertiary (Fort Union) strata in 

 Black Butte. After the deposition of the White River series of strata, 

 the beds of this age and those of the Eocene were raised together, and 



