32 University of California Publications in Geology [Vol. 12 



time was characterized by Calastcr interlineatus (Stimpson) and 



C. oregonensis (Clark) and its varieties, had no echinoderms in com- 

 mon with the other subprovinces. In the southern areas only three 

 forms are found which extend across the Diablo Range. These are 



D. giihsii (Remond), common in the Coalinga region, which also 

 occurs to the west in San Benito County, and D. ashleyi (Arnold) 

 and D. gihbsii var. liumilis Kew, which are found in the Coalinga 

 district and in Santa Barbara County. Within the subprovinces them- 

 selves different localities possess slightly different forms, as is shown 

 in the many subspecies of A. arnoldi (Pack), all of which are of 

 approximately the same age. The above evidence seems to indicate 

 that the fauna, though probably living in more or less connected sub- 

 provinces, shows marked evidence of an influence due to segregation 

 under varying environmental and climatic conditions which has 

 caused in large part at least, the dissimilarity in character of each 

 fauna ; conversely, it may be stated that tlie echinoderms quickly 

 adapt themselves to different conditions. 



During the Pliocene the Colorado desert in the vicinity of the 

 Salton Sea and Imperial Valley existed as a separate province, in 

 which the fauna was entirely unlike any other found in California. 

 This was a distinctly warm water type, which bears a close resemblance 

 to the Recent fauna of the west coast of Mexico, Central America, 

 and the Gulf of California. 



FAUNAL RELATIONS WITH OTHER PROVINCES 



In the discussion of the relationships which the Pacific Coast fauna 

 bears to that of other provinces it would be advisable to compare it 

 Avith that of other North American provinces and those of Asia. Un- 

 fortunately, so little is known of the east Asiatic fauna tliat a com- 

 parison with this province is not feasible, but the provinces of central 

 and eastern North America and of India can be satisfactorily con- 

 trasted. Tlie west coast fauna described in this paper is for the most 

 part of a type characteristic of temperate waters, except that of the 

 Gulf of California, which is tropical. In the comparison of the faunas 

 of the various provinces this fact must be kept in mind. 



The Upper Cretaceous fauna of the Avest coast possesses only three 

 genera in common with the interior and gulf provinces of North 

 America. These are Cidaris, Catopygiis, and Hemiaster, of which no 



