256 University of California Publications in Geology [Vol. 10 



a group especially well represented in the earlier Pleistocene of 

 western North America. From the White Bluffs localities the only 

 determinable specimens representing the horse family belong to an 

 advanced or specialized species of the genus Equus. In the widely 

 known North American occurrences of Equus there is as yet no 

 reported discovery of a species of such an advanced type in beds 

 earlier than Pleistocene. 



It is quite certain that the evolution stages of the horses rep- 

 resented by the Ellensburg and White Bluffs specimens belong to 

 widely different periods, of which the White Bluffs stage is the 

 later. The Ellensburg formation is evidently Miocene to early Plio- 

 cene in age ; the White Bluffs exposures represent a distinct and 

 considerably later stage in the history of sedimentation in the eastern 

 Washington region. 



It is the purpose of the following paper to give a brief statement 

 concerning the physiographic and geologic features and the fauna 

 of the White Bluffs exposures, which are here described as the 

 Ringold formation. 



Owing to brevity of the time spent in the Ringold area by the 

 writers, data concerning structure of the formation, extent of the 

 area occupied, and stratigraphic relations to the Ellensburg formation 

 must be considered incomplete. 



PREVIOUS KNOWLEDGE 



The White Bluffs section was considered by I. C. Russell 1 "the 

 most typical section of the John Day beds to be seen in Washington." 

 As the name John Day was used by Russell with reference to the 

 formation now known as the Ellensburg, it is to be presumed that 

 he considered the White Bluffs approximately contemporaneous with 

 the Ellensburg. The exposures were stated by Russell to range up to 

 500 feet in height, and to be composed of approximately horizontal 

 or only slightly tilted strata. The beds were reported to consist of 

 fine sands, clays, and strata of volcanic ash. A section taken at the 

 southern end of the cliffs measured 496 feet in thickness. 



Russell - reported that fossil bones of large animals had been 

 found in the White Bluffs beds, but that their significance was not 

 known. The exposures were considered favorable ground for collect- 

 ing vertebrate remains. Reference was made to deposits presumed 



1 U. S. Geol. Surv. Bui. no. 108, p. 97, 1893. 



2 Ibid., p. 98. 



