Vol. IX] SMITH— CLIMATIC RELATIONS 125 



Introduction, 



The Tertiary and Quaternary formations of the West Coast 

 of North America offer peculiar advantages for the study of 

 climatic relations, for they are strung out along the coast 

 from the equator to the boreal regions, and their faunas and 

 floras may be compared with Recent faunas and floras in the 

 same latitudes. 



The Recent faunas of the West Coast, from the Galapagos 

 Islands and Panama northward to Alaska, are well known, 

 in publications and collections. The climatic conditions under 

 which they live are known, and the range of species with 

 reference to temperature of the water has been determined. 

 By comparison with Recent faunas of the same region the 

 climatic conditions (temperature) of a fossil fauna may be 

 estimated, and the position of the isotherms plotted, with con- 

 siderable accuracy. This accuracy naturally decreases as we 

 go back in time, and the number of Recent species in the 

 fossil fauna decreases to little or nothing. There are nearly 

 400 Recent species in the Quaternary faunas of the West 

 Coast; of these nearly 100 range down into Pliocene, and 

 over 50 into Miocene. No Recent species ranges back to 

 Eocene, but most of the genera of that age are still repre- 

 sented somewhere in the world, and make possible accurate 

 conclusions concerning the physical conditions of that time. 



The writer has arranged at Stanford University an exhibi- 

 tion set of the marine faunas of the West Coast, from Eocene 

 to the present, and from the equator to the Gulf of Alaska. 

 This set corresponds to the accompanying correlation and 

 climatic chart, the successive faunas being placed in parallel 

 columns, so that each fossil fauna is in line with the cor- 

 responding Recent fauna of the same latitude. 



The major geographic divisions used were as follows, from 

 south to north: (1) Lower California and the Gulf of Cali- 

 fornia; (2) Southern California; (3) Middle California; 

 (4) Puget Sound; (5) Alaskan Gulf. The material in the 

 exhibition set is necessarily not so detailed as that in the lists 

 given below. And in these lists no attempt at completeness is 

 made. Only those forms are listed that are really character- 

 istic, that tell a definite story as to geographic range or 

 geologic age. 



