1915] 



Clark: Fauna of the San Pablo Group 



443 



Neocene by the Etchegoin, Merced, Purisima, Wildcat, and Fernando 

 groups, and by the San Pedro and San Diego Pliocene. 



(3) The fauna of the San Pablo group of Middle California is 

 divisible into two major zones. These are quite distinct as shown by 

 the mollusks and the echinoderms. Each of the zones is again divisible 

 into minor faunal zones which are based largely upon the restricted 

 range of echinoderm species, but in part upon the similarly restricted 

 range of some of the mollusks. 



(4) The San Pablo deposits are for the most part of true marine 

 origin. In certain sections, however, beds are found at different levels, 

 which appear to have been deposited under estuarine, brackish-water, 

 or questionably fresh-water or land conditions ; these appear to repre- 

 sent local uplifts about the border of the basin of deposition. 



(5) The temperature of the San Pablo sea was about the same as 

 that of the waters now found along the coast of Middle California be- 

 tween Point Conception and Santa Barbara. 



(6) A large percentage of the extinct species in the San Pablo are 

 closely allied to species living on the California coast at the present 

 time, the latter forms being descended from the earlier species. 



(7) The age of the San Pablo group is believed to be Upper Mio- 

 cene ; this is determined first, by the low percentage of Recent species 

 in the group ; and, second, by evidence afforded by the vertebrate 

 material found above and below the group. 



(8) The San Pablo beds of Middle California are correlated with 

 the Santa Margarita formation in San Luis Obispo County as de- 

 scribed by Fairbanks, and with the beds mapped as Santa Margarita 

 in the Coalinga oil field and in the southwest end of the San Joaquin 

 Valley. 



(9) The San Pablo group is distinctly older than the Etchegoin, 

 Purisima, Merced, Fernando, and Wildcat formations, and older than 

 the San Pedro and San Diego Pliocene. 



