18 Field Museum of Natural History — Geology, Vol. IV. 



brown sandstones from the upper red clays. The lower series was 

 designated* by C. A. White as Bridger and treated as a continuation of 

 that series from the better known Bridger Basin. The upper series was 

 designated! by King as true Uintah. The lower series was further 

 subdivided! by Peterson into two horizons designated as A and B , while 

 the upper series or true Uintah was designated as horizon C. 



The correlation of the Uintah formation with other Tertiaries has 

 proceeded slowly as evidence has from time to time been adduced from 

 itc fossil fauna. The fauna has hitherto been best known from the 

 middle and upper measures. Scott, in his admirable monograph on 

 the Mammalia of the Uintah formation, concludes by pointing out its 

 affinities with the Bridger, or middle Eocene, fauna. At the same time 

 he confirmed the generally accepted view that the Uintah group should 

 be placed at the summit of the Eocene, forming the transition to the 

 White River Miocene. Osborn, in his "Age of Mammals," has put 

 forth a careful series of correlations between the Bridger and Washakie 

 horizons on the one hand and the Uintah formation on the other. 



It is the purpose of this paper to bring out a little known titanothere 

 fauna from the middle and lower horizons and to add something in 

 detail concerning the range of various fossil forms. In connection with 

 this the following notes on the stratigraphy of the Lower Uintah Beds 

 are offered in order to more clearly define the known range of these 

 forms. 



The subdivision of the Lower Uintah Beds has been somewhat 

 vague, owing to the absence of strata which could be defined or traced 

 through any considerable distance. As will be seen, the sandstone 

 systems are chiefly of fluviatile origin and though often numerous and 

 massive, the ledges are of limited lateral extent. They therefore offer 

 no well marked datum -planes. These heavy ledges of river sandstones 

 are the chief fossil-bearing horizons of the lower Uintah. Being often 

 separated by long barren stretches, it is only with great difficulty that 

 fossil-bearing levels can be traced from one locality to another. It 

 therefore appears necessary to base the subdivisions upon faunal dis- 

 tribution — the method resorted to in nearly all inland Tertiaries. 

 While employing this method of subdivision the present writer will 

 depart from the accepted classification only so far as is necessary in 

 making clear distinctions. 



The White River Canyon offers the most favorable opportunity for 

 examining the strata of the lowermost Uintah horizon. A fissure 



* Hayden Survey, 1876, p. 37. 



fU. S. Geological Exploration of Fortieth Parallel, Map 1. 



§ Bull. Amer. Mus. Vol. VII, pp. 72-74. 



