88 The Bad'land Formations of the Black Hills Region 



Muridae — Ancestral rats and mice. 



Eumys elegans, Leidy. 

 Leporidae — Ancestral hares and rabbits. 



Palaeolagus haydeni, Leidy. 



Palaeolagus turgidus, Cope. 

 Upper Oligocene. 



Castoridae — Ancestral beavers. 



Steneofiber nebrascensis (Leidy.) 

 Lower Miocene. 



Castoridae — Ancestral beavers. 



Euhapsis brachyceps, Peterson. 



Euhapsis gaulodon, Matthew. 



Steneofiber pansus, Cope. 



Steneofiber fossor, Peterson. 



Steneofiber barbouri, Peterson. 



Steneofiber simplicidens, Matthew. 



Steneofiber sciuroides, Matthew. 



Steneofiber brachyceps, Matthew. 

 Geomyidae — Related to pocket gophers. 



Entoptychus formosus, Matthew. 



Entoptychns curtus, Matthew. 

 Leporidae — Ancestral hares and rabbits. 



Lepus primigenus, Matthew. 



Lepus Primigenius, Matthew. 

 Upper Miocene. 



Castoridae — Ancestral beavers. 



Eucastor (Dipoides) tortus, Leidy. 

 Mylagaulus — ( ?) 



Mylagaulus monodon, Cope. 



RHINOCEROTOIDEA 



The finding of fossil bones of true rhinoceroses in the Big* 

 Badlands by Alexander Culbertson in 1850, and their prompt 

 and accurate identification by Leidy, constitute one of the most 

 interesting, unexpected, and instructive paleontological discov- 

 eries of America. 



Existing rhinoceroses are confined to Africa, the Indian 

 Archipelago and the southern parts of Asia. These form but 

 a small remnant of a numerous ancestry that abounded in North 

 America from middle Eocene to late Miocene time and in Europe 

 from Eocene to Pliocene time. 



