454 University of California Publications in Geology [Vol. 11 



Several peculiarities of the Barstow fauna in comparison with 

 other assemblages of nearly the same age inside and outside the Great 

 Basin are not readily explained. With a considerable collection from 

 the Barstow region, as yet no remains representing rhinoceroses have 

 been seen, while they are known from the nearly allied Cedar Moun- 

 tain and Santa Fe faunas. As this group was present in America 

 until Pliocene time its absence from the Barstow region may be due 

 to some peculiarity of the environment. It should be noted that 

 rhinoceroses are also unknown in the Ricardo fauna. 



Another peculiarity is the absence from the Barstow of Merycodus 

 furcatus well represented in the Santa Fe beds. In the Cedar Moun- 

 tain region both types of Merycodus are present, as are also rhinoc- 

 eroses. The absence of these forms from the Barstow was possibly a 

 peculiarity of this geographic area in Upper Miocene time. 



Considering its relation to the recognized Middle Miocene of the 

 Mascall and Virgin Valley, to the Pliocene of the Rattlesnake and 

 Thousand Creek, and to the Upper Miocene of the Santa Fe, the 

 position of the Barstow fauna evidently falls within the Upper Mio- 

 cene. The position of the Barstow stage with reference to other 

 Miocene faunas of the Great Basin and adjacent regions is approxi- 

 mately as follows : 



Period 



Great Basin 

 Province 



Great Plains 

 and Rocky Mt. 

 Province 



Asia 



Europe 



Upper 

 Pliocene 





Blanco 





Lignites of 

 Casino 



Lower 

 Pliocene 



Thousand Creek 



Rattlesnake 



Ricardo 



Snake Creek 



Hipparion 

 fauna of China 

 and Siwaliks 

 in part 



Hipparion 

 fauna of 

 Pikermi 



Upper 

 Miocene 



Barstow 



Cedar Mountain 



Santa Fe 





La Grive- 

 Saint Alban 



Middle 

 Miocene 



Mascall and 

 Virgin Valley 



Pawnee Creek 





Sansan 



Sables de 

 1 'Orleanais 



The Snake Creek fauna 223 of western Nebraska shows some inter- 

 esting resemblances to that of the Barstow. In the Ecpiidae, which 



22" Matthew, W. D., and Cook, H. J., A Pliocene Fauna from Western Nebraska, 

 Bull. Amer. Mus. Nat. Hist., vol. 26, pp. 361-414, 1909. 



