94 OKIGIN OF LIFE IN AMEEICA 



amphiaetus, Japanese species are found to occur in approxi- 

 mately the same latitude on the American coast, without 

 obvious connection by way of Alaska. 



The Black Stream of Japan, the " Kuroshiwo," comparable 

 to the Gulf Stream of the Atlantic Ocean, keeps outside the 

 island chain of the east coast of Asia, sldrts the Aleutian 

 Islands, and then makes itself felt on the south coast of 

 Alaska. The fish fauna of the northern Sea of Japan has 

 nineteen per cent, of species in common with the south coast 

 of Alaska. With the Bering Sea the latter has about twice 

 as many fishes in common. All of these are forms frequent- 

 ing cold seas.* 



Dr. Dallf recently expressed the opinion, based on a 

 study of Tertiary marine deposits, that the conditions indi- 

 cated by the faunas of the post -Eocene Tertiary on the Pacific 

 coast from Oregon northward are a cool temperate climate 

 in the early and middle Miocene, a warming up towards the 

 end of the Miocene, culminating in a decidedly more warm- 

 water fauna in the Pliocene, and a return to cold, if not prac- 

 tically arctic, temperature in the Pleistocene. Further south, 

 on the Californian feoast, the Tertiary marine faunas, espe- 

 cially those of San Pedro, have been very carefully studied 

 by Professor R. Arnold. The Pliocene fauna, he remarks, 

 though not quite similar to the fauna at present living off 

 San Pedro, still contains many species which now only occur 

 north of that locality. Many of these northern species are 

 limited in range to the boreal waters north of Puget Sound. 

 Hence he concludes that these Pliocene deposits were laid 

 down in water much colder than that now found off San Pedro. 

 In the lower beds of the Pleistocene, he continues, the cold 

 climatic conditions prevalent during the later Pliocene were 

 giving place to a warmer climate, which had its effect on 

 the boreal species of San Pedro. Southern species gradually 

 increase in number -while northern ones become scarcer. 

 Finally the upper Pleistocene beds contain 14'2 per cent, 

 of species that are only now found living south of San Pedro, 



* Schmidt, P., " Verbreitung der Eische im Stillen Ocean," p. 564. 

 t Dall, W. H., "Climatic Conditions at Nome," p. 457. 



