92 Annals of the Carnegie Museum. 



There have been since then, two general names for the Tertiary of 

 the western plains, but an attempt to more closely correlate the 

 American with the European horizons has gradually led to the placing 

 of the Loup Fork in the Miocene and the White River in the Oligo- 

 cene — at least the portions of them that contained the greatest num- 

 ber of fossils — though there are beds in this region above the rich 

 fossil-bearing beds of the White River and beneath the typical Loup 

 River which, until recent years, have not yielded many fossils. 



Nearly parallel with the development of our knowledge of the 

 Tertiary of the region of the western plains, there has progressed, 

 though on a less extended scale, the study of the John Day beds and 

 their interesting faunae and florae. Though undoubtedly the lower 

 beds in the John Day region are contemporaneous with portions of 

 the White River, and are Oligocene in age, yet part of the fauna of 

 the former has appeared to be of later date and earlier than the typi- 

 cal Loup River — earlier, even, than the Loup Fork in its extended 

 sense. So in tables of the Tertiary strata of the western interior 

 region about the following succession has come into current use : 



T rr i I? .- f Nebraska beds, 



r Loup bork -Formation.. < _ ' 



I Deep River beds. 

 Miocene., j TT 



( Upper, 



[John Day Formation....^ Middle, 



Lower. 

 Protoceras beds, 



Oligocene { White River Formation^ Oreodon beds, 



I Titanotherium beds. 



Dr. J. C. Merriam, 16 in 1901, divided the John Day series into 

 lower, middle, and upper. In the lower division no good fossils were 

 found. Among the fossils in the middle division are Diceratherium 

 and Eporeodon. The latter is much like some of the Merycoidodonts 

 of the Protoceras beds (Upper White River). The upper beds of the 

 John Day series are those from which were obtained the large 

 Merycoidodonts which have been referred to Merycochoerus, but which 

 are now known as Promerycochcerus. 



In the valleys of Montana several formations have been found, 

 which, as the fossils were such that they could not be exactly cor- 

 related with other horizons, have been given various local names until 

 their position could be determined. They range from Lower Oligocene 



15 " A Contribution to the Geology of the John Day Basin," Bull. Dept. of GeoL, 

 University of Cal., Vol. 2, No. 9, p. 293. 



