20 Bulletin American Museum of Natural History. [Vol. XII, 



Deep River (Cope and Wortman) or Loup Fork (Scott), is 

 separated from the lower beds by a basaltic flow. Dr. Wortman 

 has recently found sufficient differences in the true John Day 

 to warrant its division into two horizons ; the upper, containing 

 a great abundance of Merycochmrus, being exposed at Bridge 

 Creek and elsewhere ; the lower, typical at the locality known as 

 * The Cove.' ' 



Deep River Basin. — In central Montana. It would seem to be 

 an outlier of the Great Plains basin. The upper beds, containing 

 the typical Deep River fauna, rest unconformably on beds con- 

 taining a scanty fauna which Scott considers equivalent to the 

 Upper John Day. The facies of the fauna does not seem, how- 

 ever, to forbid placing it as equivalent to the Leptauchenia fauna 

 of the Great Plains." 



Netii Mexico Loup Fork Basins. — A number of small scattered 

 areas, of which the Santa Fe Basin in the northern part of the 

 state, and the San Francisco Basin in the southwest corner, are 

 the most important. Some of these deposits may be Pliocene. 



The Pleistocene fossil beds are scattered over all parts of the 

 West, and cannot be grouped into any definite areas. The Equus 

 Beds, largely river sediments, contain abundant remains of Equus. 

 The prairie loess, so far as the writer is acquainted with it, repre- 

 sents a later deposit, aeolian, and still in progress. The wind cuts 

 out all exposed places at a very considerable rate, as may be 

 seen by the rapid hollowing out of roads and ploughed fields. 

 The dust is caught by the sodded prairie and spread uniformly 

 over it. The effects of this mode of deposition are characteristic 

 and curious features of the plains. The deposits are over two 

 hundred feet thick in places, and contain remains of Equus in the 

 lower layers, but in the upper chiefly Bison bones in various 

 stages of fossilization. In the Cordilleras are many dried-up 

 lake basins of small size, in the deposits of which the Equus 

 fauna has been found. Silver Lake in Eastern Oregon is the 

 most noted of these. 



^ Authority, Wortman (communicated). - Scott, "Mammalia of the Deep River Beds." 



