COAST RANGE CORRIDOR IN CALIFORNIA 169 



In summary: Geological data conclusively demonstrate that the 

 Central and Southern Coast Ranges were formed largely from sub- 

 marine portions of the continental shelf. The Coast Ranges then 

 constituted a land bridge between northern and southern California, 

 because a San Joaquin embayment to the east persisted as a marine 

 barrier well into the Pleistocene. Later withdrawal of the sea from 

 the embayment reduced the barrier potential between the Coast 

 Ranges and the Sierra Nevada, but the low, wide, dry valley re- 

 mains an effective barrier to many terrestrial organisms. 



There is no doubt that the Central and Southern Coast Ranges 

 eventually formed a connecting bridge around the seaward side of a 

 great structural depression, but the connection remained incomplete 

 near the southern end until Mid- Pleistocene time. The area of the 

 bridge is cut lengthwise by one of the world's major faults, the San 

 Andreas. However, the movement along the fault is largely hori- 

 zontal, and although there may have been horizontal displacement 

 of several hundred miles in the Plio-Pleistocene, it is thought that 

 the zoogeographic effect of the fault movement was negligible. Only 

 after the second peak of Coast Range orogeny, accompanied by 

 continental uplift, did the land connection become a continuous 

 bridge or corridor available to the herpetofauna. 



The original point of view here presented is that the land connec- 

 tion existed prior to the mid-Pleistocene as a large peninsula broadly 

 connected northward to the continent, as a continuous zoogeographic 

 (if not geographic) unit, and with an effective marine barrier in the 

 form of a wide strait at the southern tip. The barrier remained until 

 mid-Pleistocene time. At this time the Central and Southern Coast 

 Ranges became an effective corridor for the dispersal of many ter- 

 restrial organisms. 



During late Miocene and early Pliocene the peninsula was largely 

 occupied by Neotropical and Madro-Tertiary geofloras. The Arcto- 

 Tertiary geoflora was excluded and along with it the associated 

 herpetofauna, on the basis of purely climatic control. At the same 

 time, herpetofauna of Mexican origin and associated with the 

 Madro-Tertiary geoflora may have been unable to reach the evolv- 

 ing peninsula because of the marine barrier at the southern tip. The 

 barrier, however, was not effective in limiting the northward exten- 

 tion of the Neotropical and Madro-Tertiary geofloras. The above 

 hypothesis is strengthened by the fact that no endemic species of 



