438 University of California Publications in Geology [Vol.10 



Republican Eiver Fauna 



Aelurodon saevus (Leidy) 

 Aelurodon wheelerianus (Cope) 

 Dinoeyon maeandrinus Hatcher 

 " Machaerodus " catocopis Cope 

 ?Maehaerodus crassidens Cragin 

 Cynomys, sp. 

 Dipoides tortus (Leidy) 

 Mylagaulus sesquipedalis Cope 

 Mylagaulus monodon Cope 

 Epigaulus hatcheri Gidley 

 Lepus, sp. 



Tetralophodon euhypodon (Cope) 

 Tetralophodon campester (Cope) 



Peraceras supereiliosus Cope 

 fAphelops malacorhinus Cope 

 Hypohippus, sp. 

 Protohippus profectus Cope 

 fNeohipparion retrusum (Cope) 

 Prosthennops serus (Cope) 

 ?Merycochoerus, sp. 

 ?Merychyus, sp. 

 fProcamelus prehensilis (Cope) 

 Proeamelus, sp. div. 

 Pliauchenia minima Wortman 

 Pliauclienia, sp. max 

 Merycodus, sp. 



Teleoceras fossiger (Cope) 



The presence in the Repuhlican River of Mylagaulus, Aphelops, 

 Merycodus, and several oreodonts strongly suggests Miocene age. 

 Aelurodon wheelerianus is much like the common Aelurodon from the 

 Barstow. Other forms as Dipoides and Neohipparion are Pliocene 

 types. Matthew and Cook consider this fauna older than Snake Creek, 

 and it is evidently near the horder line between Miocene and Pliocene. 



The Loup River 1 ' 1 or Nebraska, formation of Nebraska contains a 

 fauna which has certain Pliocene types as Dibelodon (Stegodon) 

 mirificus, and possibly Hipparion, apparently of the same horizon with 

 Ecjuus and Elephas. This assemblage represents a stage near that of 

 the Idaho or Tulare, or perhaps somewhat later. More information 

 is necessary before a judgment as to the composition and age of this 

 fauna can be given. 



Of the several Great Plains faunas there can be no doubt as to 

 relative position of the two elements of largest importance : the Blanco 

 is clearly younger than the Snake Creek. If the Loup River is Plio- 

 cene it is evidently younger than the Blanco, and if the Republican 

 River fauna be included in the Pliocene it is older than Snake Creek. 

 The sequence then appear as follows: 



??Loup River Equus-Elephas zone 



Blanco Pliohippus simplicidens-Boraphagus zone 



Snake Creek Hipparion-Tragocerus zone 



*?Republican River Peraceras-Protohippus zone 



Atlantic Province 

 In the region east of the Mississippi, Pliocene mammal remains 

 sufficient to constitute a basis for study are known in the Alachua 



17 Leidy, J., Extinct Mammalian Fauna of Dakota and Nebraska, pp. 13 and 

 255, 1869.' 



