FEATURES IN HISTORY OF LIFE ON PACIFIC COAST 

 former contains a fauna like that of the Mid- 

 dle Miocene Mascall of the John Day region. The 

 fauna of the Thousand Creek beds is entirely dif- 

 ferent from that of the Virgin Valley formation and 

 most closely resembles the Pliocene life of the John 

 Day region. In the Thousand Creek fauna are a 

 number of peculiar types not previously known in 

 America, including certain twisted-horned antelopes 

 which in many respects resemble some of the living 

 African forms, and correspond approximately in 

 the type of their horns to certain widely distributed 

 antelopes of the late Miocene and early Pliocene of 

 Europe and Asia. 



Next to the John Day region of eastern Oregon 

 the most important succession of mammalian faunas 

 in the Great Basin Province is found in the Mohave 

 Desert. At least three faunas are known in the bad- 

 land deposits of this region. 



The oldest mammal-bearing beds of the Mohave 

 Desert are the extensive deposits of the Barstow 

 formation near the town of Barstow. This fauna 

 represents an Upper Miocene stage not known else- 

 where in the region west of the Wasatch. The Bar- 

 stow fauna includes about thirty species among 

 which the most common forms are three-toed horses 

 of the Merychippus type, camels of two groups, 

 primitive deer-antelope, four-tusked mastodons, 

 dogs of the heavy-jawed Aelurodon type, and large 

 tortoises. 



A second faunal stage, evidently occurring in a 

 second geologic formation of the Mohave Desert, 

 appears in the splendid exposures at Ricardo on the 

 western side of the El Paso Range, and facing the 

 foot of the Sierras. The Ricardo fauna contains 

 mammalian types of the same groups as those 

 represented at Barstow, but many of the genera and 

 nearly all of the species are different and of more 

 specialized stages. The Ricardo fauna is most 

 closely related to that of the Lower Pliocene. It 

 contains several forms, especially the horses of the 

 Hipparion group, which closely resemble species 

 found in fossil beds of the Old World. 



A third fauna of the Mohave is found in the 

 Pleistocene of Manix Lake, near Manix station on 

 the Salt Lake Railway in the eastern part of the 

 desert. The mammalian remains at this locality are 

 scattered and fragmentary, but represent the most 

 satisfactory assemblage of Pleistocene forms known 

 in the Mohave Desert area. They include two 

 horses of the genus Equus, two extinct camels, a 

 proboscidean, an antelope, and several birds. A 

 number of fresh-water molluscs are also found here. 

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