280 University of California Publications in Geology [Vol. 12 



Cretaceous, Eocene, and Miocene time occurring in the present Santa 

 Ana Range, certain old topography* of whose crest has been tenta- 

 tively correlated with the Perris peneplain. Some seventy miles to 

 the southwest of this sedimentary area lies Los Angeles and the well 

 known Pleistocene asphalt deposit of Rancho La Brea. Eastward, 

 within the San Gorgonio Pass, fossil-bearing strata^ of Mexican Gulf 

 relationship occur, deposited, it is supposed, by a far-flung arm of 

 the Gulf of California. 



Fig. la. Map showing the position of the San Timoteo and Eden deposits in 

 relation to the more important of the previously known Pliocene fossil mammal 

 deposits lying west of the Mississippi Eiver. 



Bordering as it does on all three of the so-called provinces, viz., 

 the Great Basin, the Pacific Coast, and the Gulf of California, the 

 region occupies a strategic position on the geologic map of California. 

 It is the most southern of the areas from which vertebrate remains 

 have so far been reported from the Pacific slope. 



The exploration resulted in discovery of many new and interesting 

 species described in the following pages, and in the recognition and 



* Dickerson, E. E., oil. ext., p. 259, 1914. 



5 Vaughan, F. E. Evidence in San Gorgonio Pass, Riverside County, of a late 

 Pliocene extension of the Gulf of California. Read at the meeting of the Pacific 

 Coast division of the Palaeontological Society in April, 1917. 



