440 University of California Publications in Geology |_ VoL - 10 



tains horse types near those of the Rattlesnake-Thousand Creek stage 

 and is of approximately the same age. 



The Chanac Hipparion gratum tehonense stage of the Pacific Coast 

 province is nearest to the Ricardo of the Great Basin, but not neces- 

 sarily identical with it. 



The relationship of the Pacific Coast and Great Basin Pliocene 

 sequences is approximately as shown in the table on page 443. 



Comparison of the series of Pliocene mammal faunas of the Great 

 Basin-Pacific Coast scale with that of the Great Plains and Atlantic 

 provinces should not be expected to show a large percentage of com- 

 mon specific types, even if the time of deposition be approximately 

 identical, as important physical barriers intervened and specific range 

 would presumably not be much wider in America of the Pliocene than 

 at present. 



In a comparison of the Great Plains sequence with that in the 

 provinces west of the Wasatch there is noticeable at once a similarity 

 of the Blanco and Upper Etchegoin horses, and of the Blanco canid 

 of the Borophagus type and HyaenognatJius presumed to be of Tulare 

 age. There seems good reason for considering the Blanco and Upper 

 Etchegoin faunas as of nearly the same stage. The Tulare, which 

 immediately follows the Upper Etchegoin, may approximate a late 

 stage of the Blanco. 



The Snake Creek fauna of western Nebraska contains a consider- 

 able number of forms corresponding approximately to those of the 

 Ricardo stage of the Great Basin province. The Snake Creek horses 

 include species of Plioliippus and Hipparion at least as advanced as 

 those of the Ricardo. The artiodactyls of the Snake Creek include 

 Mcrycodus and advanced oreodont forms as in the Ricardo. With 

 the advanced horses there are, however, noted certain primitive 

 forms as Merychippus and Parahippus, and with artiodactyls of 

 the Merycodus type some advanced antelopes are also represented. 

 If, as seems possible, the Snake Creek fauna represents more than 

 one stage, it is to be presumed that one of the horizons is not far from 

 the stage of the Ricardo. It is possible that another horizon in the 

 Snake Creek beds might correspond to the stage of the Rattlesnake, 

 Thousand Creek, and Middle Etchegoin. 



The Republican River fauna of northwestern Kansas represents a 

 stage recognized as near the beginning of the Pliocene. Matthew and 

 Cook, 10 who have made a most careful comparison of this assemblage 



is Matthew, W. D., and Cook, H. J., Bull. Amer. Mus. Nat. Hist., vol. 26, 

 p. 368, 1909. 



