474 



Annals of the Carnegie Museum. 



beds in this locality, as recently determined, can be of no greater ver- 

 tical thickness than 150 to 200 feet. 



The beds are exposed for four or five miles along the south side of 

 the Running Water or Niobrara River a few miles east of the Wyoming 

 and Nebraska State line. In the section shown in Fig. 3 the Nebraska 

 beds have a thickness of about 70 feet. There are considerable ex- 

 posures of the Nebraska beds on the south side of the Running Water 

 River, and in places they have a vertical thickness of perhaps 200 

 feet. 



Some fifteen rniles south of the Running Water there is a series of 

 exposures overlying the Nebraska beds. These exposures are un- 

 doubtedly the Ogalalla beds of Darton. No work was done in them 

 by our party and their relation to the section here published is not 

 sufficiently known to the writer to warrant any further mention. 



The accompanying geological section extending from Squaw Butte 

 on the northern face of the Pine Ridge which marks the northern 

 limits of these beds at this locality, in an imaginary line southward 

 for 15 miles, to the Running Water River represents the sequence of 

 the various Loup Fork horizons in this region. The latest divisions 



J^ehrasha 





Fig. 3. Ideal section of jSIiocene formations from Squaw Butte to south side of 

 Running Water River, Sioux Co., Nebraska. 



and names proposed by Darton and Hatcher are used for the various 

 horizons in the accompanying section (Fig. 3) and are believed, by 

 the writer, to be the most satisfactory classification yet proposed of 

 the Miocene beds in this locality. In the Gering horizon no fossil 

 remains have been collected. The upper part of the Monroe Creek 

 horizon has yielded some material, as has also the Harrison beds. 

 The uppermost part of the section, or the Nebraska beds are appar- 

 ently the richest in vertebrate fossils of the entire series. From this 



