Vol. 6] Merriam: Virgin Valley and Thousand Creek. 



207 



has not been known from the typical locality of the Mascall, 

 but has recently been noted by the writer in Mascall collections 

 from the Crooked River region, south of the Blue Mountains in 

 Oregon. At the type locality of the Mascall one other horse 

 with short-crowned cheek-teeth (Archaeohippus) is represented. 

 Merychippus is the most common horse in both the Virgin Valley 

 and the Mascall. and Pliohippus is apparently absent from both 

 faunas. The Pliohippus specimens reported from the Mascall are 

 doubtful. Tephroeyon, the most characteristic carnivore of 

 Virgin Valley, and Mylagaulus, the most characteristic rodent, 

 are both included in the Mascall fauna. 



With Pawnee Creek the Virgin Valley ungulate fauna has a 

 large percentage of forms in common. In both faunas Hypo- 

 hippus, Parahippus, and Merychippus are present without ac- 

 companying Pliohippus. The genera Moropus, Mevyeh yus, Blas- 

 tomery.r and Merycodus appear in both, while the rhinoceroses, 

 mastodons and camels are suspiciously similar. Mylagaulus 

 appears in both faunas, and some of the Pawnee Creek canids 

 are doubtfully referred to Tephroeyon. 



The fauna of the Snake Creek Beds of western Nebraska 

 shows a remarkable similarity to that of Virgin Valley, a larger 

 percentage of Virgin Valley species being found in the Snake 

 Creek fauna than in any other assemblage of forms known to 

 the writer. Particularly noticeable is the practical identity of 

 several of the carnivore forms as Tephroeyon, Felis, and Pro- 

 bassariscus. The Virgin Valley Prohassariscus differs from that 

 of Snake Creek so slightly that the distinction may not be con- 

 sidered as of more than subspecifie value. The deer-like forms 

 Dromomeryx, Blast ornery x, and Merycodus appear in both 

 faunas. Among the horses Hypohippus, Parahippus, and Mery- 

 chippus are common to the two, but the abundance of more ad- 

 vanced forms of the Neohipparion and Protohippus types indi- 

 cate that the Snake Creek fauna must represent a stage con- 

 siderably later than that of Virgin Valley. The difference 

 between the two faunas presumably corresponds to a time inter- 

 val about as long as that represented by the Upper Miocene, but 

 is probably not longer than that division. 



