

South Dakota School of Mines 109 



Agriochoents latifrons Leidy. 

 Oreo don {Merycoidodon) culberts'oni Leidy. 

 Oreodon {Merycoidodon) gracilis Leidy. 

 Orcodon {Merycoidodon) sy cf bulletins Leidy. 



Upper Oligocene. 



Agriochoents major Leidy. 



Agriochoents gaudryi Osborn and Wortman. 



Agriochoents migrans Marsh. 



Eporeodon {Bucrotaphus) major Leidy 



Bucrotaphus jacksoni Leidy. 



Lower Miocene. 



Mesorcodon megalodon Peterson. 

 Promerychochoerus carrikeri Peterson. 

 Promerychochoerus vantasselensis Peterson. 

 Phenacocoelus typus Peterson. 

 Merychyus elegans Leidy. 

 "Merychyus" harrisonensis Peterson. 

 Leptauchenia decora Leidy. 

 Leptauchenia major Leidy. 

 Leptauchenia nitida Leidy. 

 Merychyus minimus Peterson. 



Of the several genera in the above list Oreodon, Leptau- 

 chena, Agriochoerus, and Promerychochoerus are the best 

 known. Oreodon is by far the most abundant, but the others 

 are found in considerable numbers. They seem to have ranged 

 in great -herds over the Oligocene and Miocene lands of South 

 Dakota, Nebraska, Colorado, Wyoming, Montana and North 

 Dakota. It is interesting in this connection to note that the 

 Oreodontidae, in addition to giving their name to the Oreodon 

 beds of the Middle Oligocene furnished names also for three of 

 the zones above the Middle Oligocene, namely, the Leptauchenia 

 zone, the Promerychochoerus zone, and the Merycochoerus 

 zone. 



Leptauchenia was founded on fossil remains obtained by 

 Prof. Hayden in 1855 from near Eagle Nest butte. This animal 

 is of interest in that its structure seems to indicate an aquatic 

 habit. The teeth resemble somewhat those of the llama 

 ( Auchenia) hence the name Leptauchenia. Agriochoerus, the 

 restored skeleton of which is reproduced in Figure 16, is remark- 



