THE PLIOCENE OF EUROPE, ASIA, AND NORTH AMERICA 357 



The mammal-bearing beds of the 'Thousand Creek' section seem to 

 correspond mainly with the upper levels of the Virgin Valley. The frag- 

 mentary fossils found here are of extraordinary interest. The two large 

 antelopes (Ilingoceros, Sphenophalos) exhibit close affinities to those of the 

 tragelaphines of the Siwaliks of Asia, including the recent nilgai (Bosela- 

 phus), which in turn are related to the recent kudu (Strepsiceros) , eland 

 (Oreas), etc., of Africa. The kudu (Strepsiceros) and eland (Oreas) occur 

 in the Siwaliks of southern Asia, as well as the nilgai. 



Sphenophalos presents a near resemblance to the Neotragocerus discovered 

 in the Snake Creek beds, Nebraska (p. 355) , except in the comparative smooth- 

 ness and denseness of the surface of the horn core, which suggests affinity 

 to the recent prong-horn antelope (Antilocapra) of the Western plains. 

 If this animal (Sphenophalos) proves to be intermediate between the bovine 

 antelopes of Asia and our prong-horn antelopes, or antilocaprids, it will go 

 to confirm the theory advocated by Matthew ^ that the American prong- 

 horns are, after all, aberrant antelopes, that is, with affinities to the 

 Bovidae. 



The true antelopes are represented by Neotragocerus, as well as by 

 three species of the two Asiatic genera above mentioned. 



A rich fauna of typical American mammals was contemporaneous with 

 these antelopes in Nevada, and points to their Lower Pliocene age, espe- 

 cially in the survival of several species of rhinoceroses and the stage of horse 

 evolution known as Merychippus and Parahippus. The forest-living horse 

 (Hypohippus) and the desert-living type (Neohipparion) are somewhat 

 doubtfully recorded. Among the aberrant Perissodactyla is a form at- 

 tributed to Chalicotherium. The peccaries are represented by Prosthennops; 

 the cameloids by Procamelus and Alticamelus. There is a species of Palceo- 

 meryx near P. borealis, as well as the deer-like antelope Merycodus. 



The small fauna includes the sewellels (Haplodontia), marmots, hares, 

 mylagaulids, castoroids (Dipoides), and gophers (Geomys); beside several 

 kinds of canids there is a felid of gigantic size. 



The Edentata are represented by remains of very large claws resembling 

 those of the megalonychids except for a narrow median fissure. 



Rattlesnake Formation of the John Day Valley, Oregon 



As shown in the diagram (Fig. 164), this is the uppermost of the series 

 of Csenozoic formations in the John Day region, overlying the Middle 

 Miocene Mascall Formation and the Upper Oligocene John Day.^ The type 



' Matthew, W. D., A Complete Skeleton of Merycodus. Bull. Amer. Miis. Nat. Hist., 

 Vol. XX, 1904, pp. 101-129. 



- Morriam, J. C, and Sinclair, W. J., Tertiary Faunas of the John Day Region. Univ. 

 Cal. Publ., Bull. Dept. GeoL, Vol. V, no. 11, Oct., 1907, pp. 171-205. 



