m.l.] COPE ON HORIZONS OF EXTINCT VEETEBRATA. 47 



TAiiUNiAN. Loup Fork. 



Sip2}otherium (Oeningian). Hippotherium. 



Frotoliippus. 



Sippidium.* 

 Cmnotherium. Oreodontidce. 



AnthracotJierium. 



Falceomerxjx. Blastomeryx. 



Dicrocerus. 

 Procervulus. ' Procervulus. 



Protolahis. 



Procamelus. 



The existing genera mentioned as found in tlie Falnnian fauna are 

 paralleled by tlie I>icotijles, Systrix, and Mustela of tlie Loup Fork beds. 

 It is evident that this latter horizon retains in its Oreodontidce the same 

 traces of antiquity that the Falunian does in its Cmnotherium^ but shows 

 a more modern aspect in the omission of Anchitherium and its replacement 

 by Sippotherium and Protoliippus, and in the still more modern type Hip- 

 pidium. Although but six genera of the two continents are determined 

 as identical in the above table, yet others, which are facing on the same 

 line, are very nearly aUied. Other differences are geographical. The 

 fades of the Loup Fork horizon is then a compound of that of the Falu- 

 nian and Oeningian, or Middle and Upper Miocene. 



In commenting on the above-described fauna in 1874,t I remarked that 

 "the proper discrimination of American Pliocene remains to be accom- 

 plished." It was not long after that date that material for making the 

 identification of this horizon on this continent first came into my hands. 

 This was derived from the superior Tertiary of Oregon, and includes a 

 considerable number of species of fishes, birds, and Mammalia. I pub- 

 lished a list of some of the species in 1878.| The character of the faima 

 from that region coincides with that which has from time to time been 

 unearthed in the caves and other Eastern deposits to such an extent as 

 to lead us to suspect that the differences between them are geographical 

 only. In Europe, the Pliocene, or Subapennine, includes, according to 

 D'Orbigny (1855) and Oaudry (1878), the Plaisancian and Astian, which 

 are represented at the following locahties : 



Subapennine. 



Plaisancian. — Montpellier; Casino (Tuscany). 



^8<ta«.— Perrier, near Issoir, Coupet, Vialette (Upper Loire), Cliagny; English 

 Crag ; part of deposits of tlie Val tVArno. 



The characteristic of this fauna is the fact that the species belong 

 mostly to existing genera, the chief exception being jHiipiJo^/tmjn?!. The 

 horses are chiefly represented by Equus. Common genera are Aretomys^ 



* FUohippus Marsh. 



t Report Lieut. G. M. "VVlieeler, IV, Palfeontology of New Mexico, 1874, p. 364. 



tBuU. Hayden's U. S. Geol. Surv. Terrs, iv, 1878, p. 389. 



