HISTORY OP PACIFIC OCEAN 319 



succeeded by Miocene beds with a marine fauna. Similarly 

 he describes a series of Miocene marine mollusks from sand- 

 stones obtained at the head of the Gulf of Penjinsk on the 

 opposite shore of Asia. As in Alaska, these Miocene sand- 

 stones are apparently resting on leaf-bearing lignites, thus 

 strengthening the assumption of a wide and freely open 

 passage in the north, between the Pacific and Arctic Oceans.* 

 Professor Schuchertf separates North America from Asia by 

 a marine channel throughout Miocene and Pliocene times in 

 his maps illustrating North American paleogeography. All 

 the evidence, says Mr. Knopf,{ from which conclusions of 

 some positiveness can be drawn, record only epochs during 

 the Tertiary Era of more widely spread submergence and 

 increased separation of the continents. And yet his exten- 

 sive studies of the mammalian fauna led Professor Osborn § 

 to the conclusion that the emergence of continents progressed 

 during the Miocene Period and that North America was 

 broadly united with eastern Asia. How can we reconcile these 

 diametrically opposite views ? I have shown that in Oligo- 

 cene times, or during part of that Period,^ a trans -Atlantic land 

 connection probably enabled the Old World types to travel to 

 North America. A Bering Strait land bridge is not essential, 

 therefore, in explaining existing Oligocene or Eocene affini- 

 ties between the Old World and the New. But I have given a 

 large number of instances among North American plants as 

 well as animals, indicating a direct migration either from Asia 

 to North America or vice versa, in early and late Tertiary, at 

 any rate in pre-Pliocene times. I need only allude again to 

 the close relationship of the hellbender of the eastern States 

 to the Japanese giant salamander, of the blue-tailed skink 

 of the eastern States and Japan, and of the absolute identity 

 of the American and Japanese ground lizards (Lygosoma 

 laterale). The only living relation of the American alligator 

 inhabits the Yangtse river in China ; the nearest akin to the 

 American green snakes (Liopeltis and Cyclophis) reside in 

 south-eastern Asia. The family of snapping turtles (Chely- 



* Dall, W. H., "Miocene Fauna in Arctic Siberia," p. 473. 



t Schuchert, C, " Paleogeography of North America," Maps 98— 100. 



t Knopf, A., " Tertiary Land-connection," p. 419. 



I Osborn, H.F., " The Age of Mammals," p. 244— 245. 



