NEOCENE STRATIGRAPHY. 361 



southern forms. It thus resembles quite strongly the 

 fauna studied at San Pedro and called in this paper Plio- 

 cene. 



This case is interesting, not alone from showing that 

 the fauna considered Pliocene on the coast of the main- 

 land is still living on or about the island, but from the way 

 the fauna supports the deductions made from the topo- 

 graphy and vice versa. 



Quaternary faunas. — The faunas of the beds recognized 

 as Quaternary are so similar to existing faunas that what 

 has been said about the present distribution of species 

 along the coast will hold for the Quaternary species. 



Pliocene faunas. — The Pliocene faunas bear quite a 

 striking resemblance to the existing forms of the same 

 region, except that there are present a large number of 

 northern forms with some forms which have since become 

 extinct. Until the Pliocene has been differentiated at 

 Santa Barbara, San Diego and intermediate points, as the 

 writer believes they will be ere long, it will be unsafe to 

 generalize on the local distribution of species. 



Aliocene fauna. — The Miocene fauna, while showing 

 some regional relation to existing faunas, is principally 

 distinguished by its uniformity over the State and its 

 southern character. 



Climatic changes. — The facts given indicate that during 

 Miocene times a tropical or subtropical climate existed in 

 California. This is followed by a colder climate and the 

 introduction of boreal forms of life. The end of the Ice 

 age, presumably, brings a return of warmer conditions 

 and the northern forms return to the North Pacific, some 

 species suffering extinction under the changed conditions. 



The question arises whether the species found in the 

 Pliocene of California, which are at present living in the 

 North Atlantic, have migrated from the Pacific, or whether 



