Vol. IX] SMITH— CLIMATIC RELATIONS 167 



This shifting of the isotherms was feh as far southward as 

 Magdalena Bay, Lower CaHfornia, in the edge of the tropics, 

 for the Quaternary fauna of that locaHty, while still tropical, 

 contains many Californian species not known to occur there 

 now. 



This was the time of greatest southward shifting of the 

 isotherms and greatest lowering of temperature on the West 

 Coast. It probably corresponds to the maximum glaciation 

 on the continents of the northern hemisphere. 



A very decided rebound from the cold temperate condi- 

 tions of the lower Pleistocene is seen in the fauna of the upper 

 San Pedro formation in the Los Angeles embayment of south- 

 ern California. This fauna shows a displacement of all the 

 northern types, and the incoming of tropical forms from Lower 

 California; among them are: Dosinia ponderosa, Pecten sub- 

 nodosus, Chione gnidia, Chione neglecta, Cardium procerum, 

 Miltha childreni. This would indicate a minimum temperature 

 of nearly 68° F., a rise of about 18° F. from the lower San 

 Pedro. 



This amelioration of the climate extended up to Cape Nome, 

 for there the fossil fauna contains Pecten swifti, which now 

 lives 1200 miles to the southwest in the Japanese waters, 

 warmer by 8° F. than the present temperature of Bering Sea. 



The two extremes of climatic conditions are seen in the 

 Eocene and in the lower Pleistocene. In the former a tropical 

 climate extended up to Alaska, and in the latter a Puget Sound 

 climate stretched southward to San Diego. 



The fall and the rise were probably oscillatory rather than 

 regular, but the marine faunas do not furnish a sufficiently 

 sensitive thermometer to register the minor fluctuations. 



Basis of the Work. 



The conclusions given in this paper are based upon a critical 

 study of collections of Recent, Quaternary, and Tertiary fossils 

 made on the Pacific Coast, from Ecuador to Alaska. Material 

 was studied by the writer, or by workers assisting him, in the 

 U. S. National Museum, Philadelphia Academy of Science, 

 California Academy of Sciences, University of California, 



