Vol. VII] DICKERSON— CLIMATIC ZONES 195 



the Mt. Diablo region. It has recently been shown that the 

 Tertiary gravels of the Sierra Nevada are of Tejon Eocene 

 age.^ These gravels and interbedded clays have yielded a con- 

 siderable flora. Knowlton^ states that Laurus (4 species), 

 Per sea (3 species), Oredaphne (2 species), Cinnamomum (2 

 species), Artocarpus (2 species), Zizyphus (2 species), Ficiis 

 (6 species), and Sabalites (1 species), are tropical or semi- 

 tropical genera which are abundant in these strata. He com- 

 pares this flora to that of Florida today. In addition to these 

 are several species such as liquidambar and magnolia, charac- 

 teristic genera of the warm temperate climate. 



Valuta lazvsoni, Macrocallista conradiana, Oliverata calif or- 

 nica, Surcula crenatospira and Cardium dalli occasionally retain 

 the high coloring characteristic of many tropical genera. The 

 fauna of the Tejon contains many genera characteristic of the 

 tropics of the present day. 



Among these are Voluta, Siphonalia, Turris, Surcula, Tere- 

 hra, Canccllaria, Drillia, Architectonica, and Conus in abun- 

 dance. In addition the colonial corals, Dendrophyllia tejon- 

 ensis and Thamnasteria sinuata have been recently described 

 from the type Tejon and the Tejon of the Mt. Diablo region. 

 The ornamentation of the Tejon species is in general much 

 greater than that of the Martinez. This is explained in part 

 by a milder climate during Tejon time and by the fact that 

 the Martinez fauna is a simple Tertiary fauna as yet unde- 

 veloped. 



As was stated above there is an essential faunal unity in the 

 Los Angeles and San Francisco basins, but there are certain 

 significant differences which were particularly impressive while 

 collecting in the field. Laboratory studies confirm this. At 

 certain horizons in the Simi hills a good percentage of the 

 rocks consisted of massed Turritcllas, at other horizons Siphon- 

 alia mucronata, and Amauropsis martinezensis were particu- 

 larly abundant. One of the striking features was the occur- 

 ence in great abundance of one of the Volutidce, a form 

 described by Gabb under the name of Turhinella crassatesta. 

 This species is an exceedingly rare form in the San Francisco 



' Dickerson. R. E.. Stratigraphy and Fauna of the Tejon Eocene of California, 

 Univ. Calif. Publ. Bull. Dcpt. Geol.. vol. 9, p. 398, 1916. 



2 Knowlton, F H., in Topographic Revolution on the Pacific Coast, Fourteenth 

 Annual Report, U. S. Geological Survey, pt. 2, p. 421, 1894. 



