424 University of California Publications in Geology [Vol. 10 



the Cenozoie. We begin now to see for the first time the broader 

 world relationships of our higher vertebrate Pliocene life. 



Of American Pliocene faunas, those represented in the Pacific 

 Coast and Great Basin provinces have been so imperfectly known that 

 it seems desirable to present a general statement of their composition 

 and relationships for use in consideration of certain fundamental 

 faunal problems involved in later Cenozoie history. 



AMERICAN PLIOCENE FAUNAS 

 Pacific Coast Province 



At the present time there are known in the Pacific Coast province 

 at least four important occurrences of Pliocene mammalian remains, 

 and there are probably represented in these stations four fairly dis- 

 tinct stages or horizons. These are the upper and middle and lower 

 Etchegoin on the western border of the San Joaquin Valley ; the 

 Tulare overlying the Etchegoin of the Great Valley of California; 

 the Chanac formation of the Tejon Hills at the southern end of the 

 San Joaquin Valley, and the Pinole Tuff-Orinda section of the 

 Mount Diablo or San Francisco Bay region. Of these formations, the 

 Etchegoin- Tulare section is not less than 10,000 feet in thickness; 

 the Pinole Tuff-Orinda section represents at least 5000 feet of strata ; 

 the Tejon Hills section so far as known represents only a few hundred 

 feet of accumulation. 



The faunal sequence of the Pacific Coast region is exceptionally 

 well represented in the Etchegoin-Tulare section, but the amount of 

 material from the beds of that region is unfortunately scanty. Within 

 the limits of the Etchegoin two or perhaps three faunal zones are 

 known. There is apparently a clear distinction between the upper 

 zone characterized by the presence of Pliohippus proversus, a very 

 advanced horse like the Blanco Pliohippus, and the middle zone dis- 

 tinguished by the presence of Pliohippus coaling ensis, a typical Plio- 

 hippus. Below the horizon of P. coalingensis several fragmentary 

 specimens of Hipparion have been found, but as yet no remains of 

 hipparions are known from the P. coalingensis and P. proversus 

 zones. The lowest beds have been discussed in a tentative way as the 

 Hipparion zone. 



In the Tulare formation overlying the Etchegoin no certainly 

 authenticated occurrences of mammalian remains are reported. About- 



