EOCENE HORIZONS OF CALIFORNIA 



CLARENCE A. WARING 



California State Mining Bureau, San Francisco 



During the past few years geologists of California have been 

 devoting considerable attention to the Eocene, with the result that 

 three horizons are now recognizable. In order of their deposition 

 these are the Martinez, Tejon, and lone formations. 



MARTINEZ FORMATION 



The Martinez formation has so far been found in the Mt. Diablo 

 region. Contra Costa County; in the Santa Monica Mountains, 

 northwest of Los Angeles; and on the west side of the Santa Ana 

 Mountains. It is characterized by sandstones and shales, not 

 unlike those of the Chico (Upper Cretaceous) formation, and by a 

 fauna strikingly similar to those of the eastern Midway formation, 

 with which it is to be correlated. In the Santa Monica Mountains it 

 is characterized by Venericardia planicosta var. venturensis var. nova, 

 which is similar to V. planicosta Harris.^ Several other new species 

 have also been found, the most characteristic of which here 

 described are from the Santa Monica Mountains. 



Crassatellites hranneri n.sp. — Shell about 55 mm. high, trigonal, 

 slightly longer than high; beaks subcentral, prominent, deeply 

 excavated front and back, incurved, with sides sloping equally 

 and rapidly, most abrupt in advance, shghtly convex behind; 

 lunule cordate ; anterior end broadly rounded ; posterior truncated 

 and flattened from the umbonal ridge to the cardinal and posterior 

 margins. Surface marked by lines of growth and fine radiating 

 lines which are especially apparent in worn specimens. Leland 

 Stanford Junior University Paleontological Collection. Named 

 in honor of Dr. J. C. Branner. 



Lima perrini n.sp. — This giant circular lima has a thick shell 

 with nacreous, and outer prismatic layer. The diameter is about 



I Bull. Am. PaL, No. 4, p. 58, Fig. 13. 



782 



