MIOCENE. 37 



Dorcatherium ; in America, Leptomeryx, Hypertragulus, Hypisodus, and Poe- 

 brotherium. It is curious that while Leptotneryx is also European,* it has 

 not yet been found above the Phosphorites. Among Suillines, the Paloeo- 

 chcerus\ of the Oregon White River beds has also not been found below the 

 Aquitanian in Europe. But the American DidelphysX Hywnodon, Amplii- 

 cyoti, Elotherium, and Hyopotamus, with the numerous Chalicotheroid species, 

 show clearly that the White River fauna may be looked upon as a mixture 

 of those of the Stampian and Aquitanian, the former of which is sometimes 

 referred with reason to the Upper Eocene, while the latter is always left in 

 the lowest Miocene. And the solution of this question of position as 

 regards the White River beds appears to me to be at present by no means 

 €asy.§ According to the system of Naumann, it should be called Oligocene. 



Although Artiodactyles with Selenodont molars are far more abundant 

 in both continents during this period than the last, a remarkable difference 

 is to be observed between them. Those of Europe still largely consist of 

 the types with five crescents, as represented by the numerous Hyopotami 

 and Ccenotheria, while in America the modern fom*-crescent-bearing molar 

 characterizes almost the entire suborder, the only exception being two 

 species of Hyopotamus. 



The following table will represent the relations of the White River 

 fauna: 



Stampian and Aquitanian. White River. 

 Didelphys. Didelphys. 



Leptictidce. 

 ProtomyidcB Protomyid(B.\\ 



Saccomyidce.^ 



Stampian and Aquitanian. White River. 



Steneofiber. Steneofiber. 



Leporidce. Leporidce. 



* I think M. Filhol's Prodremoiherium is identical Trith Leptomeryx. 

 t Tkinohyus Marsh appears to be the same, 

 t Herpetotherium Cope ; Peratherium Aym. 



J See Ann. Report U. S. Geol. Surv. Terrs. 1878, p. 462, where the White River beds are deter- 

 inined as Lower Miocene. 

 II Ischyromya Leidy. 

 IT Enioptychua and FlearoUeus Cope. 



