250 RALPH ARNOLD 



San Diego; and the Peninsula of Lower California. The Sierra 

 Nevada and Sierra Madre and San Bernardino and San Jacinto 

 mountains may also be considered in the same class. The region of 

 Santa Catalina and San Clemente islands off southern California 

 belong to an area about which little is known previous to the Miocene, 

 although it is the belief of the writer that they are in a belt of more or 

 less persistent uplift. 



The negative elements or areas of persistent subsidence are: Puget 

 Sound; the Willamette Valley; the San Joaquin Valley, and the 

 Sacramento Valley to a less degree; central Ventura County; and, 

 since the Eocene, the Salinas Valley, and the vicinity of Los Angeles. 



