HISTORY OF 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 w© 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-Plioeene 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- 
* Dali, W. II., “Miocene Fauna in Arctic Siberia,” p. 413. 
t Schuchert, C., “ Paleogeography of North America,” Maps 98—100. 
X Knopf, A., “ Tertiary Land-connection,” p. 419. 
§ Osborn, H. F., “ The Age of Mammals,” p. 244—245. 
