South Dakota School of Mines 



43 



tions, and are exposed in the upper part of the various tributary 

 creeks.''* 



For a section of these beds see Figure 8. from U. S. Geol. 



Porcupine Butte 

 'Volcanic ash layer 



8/astomeryx 

 Parahippus 



Itferyco cheer us 

 zone 



Prctomeryx 

 Merycochcerus 

 Merychyus (abundant) 



Cajc a_reo us_s ha jy 

 mestone layers 



Promerycochaerus 

 Promery- (very abundant 

 cocTioerns and characteristic) 

 zone Diceratherium 



EJotherium 

 Steneof/ber 

 r/ypertragulus 

 Parahippus (small sp) 

 Leptauchenia 

 (near base) 



Figure S- -Columnar section from Porcupine Butte northward toward White 

 River, as observed by Matthew & Thomson. 1906. Osborn. 1909. 



Survey Bulletin Xo. 361, p. 70, Cenozoic Mammal Horizons of 

 Western North America, etc.. by Osborn and Matthew. 



THE MIDDLE MIOCEXE 

 The Middle Miocene., so far as I am aware, has not been 

 positively identified within the area covered by the Black Hills 

 map, but strata of this age have been studied fifteen or twenty 

 miles south-southwest of Agate Springs., and they have there 

 yielded a limited fauna. Matthew and Cook designate them as 



♦Matthew, W. D. A Lower Miocene Fauna from South (Dakota. 

 Am. Mus. Nat. Hist., Bull., Vol. 23, 1907, pp. 169-219. 



