Features in History of Life on Pacific Coast 

 tion. In a studj^ of the material available import- 

 ant results have been obtained which bear on the 

 evolution of the cephalopods, and on the whole 

 biological question of mode of evolution. In a num- 

 ber of cases these faunas exhibit close relationship 

 with those of the Triassic of other portions of the 

 world, and make possible important studies on the 

 geographic distribution of animals, and on climatic 

 changes during Triassic time. Extensive materials 

 representing the West American Triassic inverte- 

 brates are deposited in the palaeontologic collec- 

 tions of Stanford University. 



The rocks of the Cretaceous period are of great 

 geographic extent and of unusual thickness. At 

 Elder Creek in the northern portion of the Sacra- 

 mento Valley, California, a measured section has 

 been studied which approximates 30,000 feet in 

 thickness. Three important faunal zones, the lower 

 or Knoxville, the middle or Horsetown, and the 

 upper or Chico, have been recognized. Abundant 

 material representing all of these zones has been 

 described by W. M. Gabb, by Dr. T. W. Stanton, and 

 by F. M. Anderson. Good collections are available 

 at Stanford University and at the University of Cali- 

 fornia. The Knoxville division is by many consid- 

 ered to represent the Jurassic rather than the Cre- 

 taceous. Excellent material from Cretaceous faunas 

 is also known at many other localities in the West, 

 as in the Klamath Mountains on the border line 

 between Oregon and California, the Blue Mountains 

 of eastern Oregon, at Martinez and Mount Diablo 

 near San Francisco, and in the Santa Ana Mountains 

 in southern California. 



The marine Eocene of the Pacific Coast has one 

 of the best represented and best known of the later 

 faunas. At least two divisions are recognized, the 

 lower or Martinez and the upper or Tejon, in both 

 of which a large number of species are reported. 

 The Martinez fauna is found in the southern portion 

 of California, and possibly as far north as Wash- 

 ington. The generally recognized Tejon fauna 

 ranges the whole length of the Pacific Coast region 

 and serves as one of the characteristic bases for 

 reference in stratigraphy. The Martinez fauna is 

 well known at Mount Diablo near San Francisco. 

 The typical locality of the Tejon is at the southern 

 end of the San Joaquin Valley in California. 



Oligocene faunas are found in Oregon and Wash- 

 ington, and have more recently been described from 

 middle California. 



In the Miocene an unusual wealth of invertebrate 

 material appears in Oregon, Washington, and Cali- 



94 



