590 BRUCE L. CLARK 
Santa Monica Mountains was apparently part of an early positive 
block bordering the east-west: trough mentioned above. To the 
north of this trough the region now occupied by the Santa Ynez 
Mountains constituted the westward extension of the old Tehachapi 
peninsula. 
Po 
Fic. 3.—Meganos (Middle Eocene) 
Some of these old positive areas were so persistent throughout 
the Tertiary time that they might well be given names, following, 
on a smaller scale, the example of Schuchert in his Paleogeography 
of North America. Certain of these positive and negative areas 
have been persistent throughout all Tertiary time, while others 
were formed at a later date. Also, it is worthy of note that the 
old positive and negative areas had the same trend as the present 
mountain ranges. 
