NOETHEEN PACIFIC IN THE PAST 97 



I have endeavoured to show in this chapter how the more 

 striking instances of relationship among the animals of Asia 

 and North America can be explained, how they arose and 

 under what climatic conditions. That Alaska was once joined 

 by land to the opposite shore of Asia has been almost uni- 

 versally acknowledged by biologists and geologists. But for 

 our purpose we required something more definite than a state- 

 ment such as that of Professor Heilprin,* " it appears likeily 

 that the bears, swine, oxen, sheep, antelopes and elephants 

 originated in the Old World, whence they were transplanted, 

 by way of some land connection existing in the north^ into 

 the New World." Even Dr. Arldt's f remark, "the bridge 

 between Asia and North America remained until the Glacial 

 Period," is too vague. I think I have brought together suffi- 

 cient data to show that a land connection existed in the 

 region of Bering Strait during Pliocene times until the com- 

 mencement, or perhaps until the end, of the early part of the 

 Pleistocene Period. As far as I know, the only fact that can be 

 brought forward against such an assumption is the discovery 

 by Dr. Dall of marine gravels at Nome, in Alaska, contain- 

 ing shells which he believed to be of Pliocene Age. Consider- 

 ing, on the other hand, that the gravels in question only con- 

 tained one distinct species, it is quite possible that they may 

 not be so old as Dr. Dall thinks. And even if their Pliocene 

 age should be established by further researches, it only proves 

 that the land connection was not so wide as we are apt .tq 

 believe. These gravels do not disprove the existence of the 

 land bridge, for Nome is situated to the south of Bering Strait 

 on the shores of the Bering Sea. 



I have adduced testimony showing that Alaska, not only in 

 Pliocene times, but also during part of the Pleistocene Period, 

 had a comparatively mild climate. Many of the larger 

 mammals seem to have become exterminated within more 

 recent times owing to a change of climate. .There is no indi- 

 cation of any wholesale destruction of the fauna during the 

 Glacial Epoch followed by a recent introduction from the 



* Heilprin, A., " Geographical Distribution of Animals," p. 179. 



t Arldt, Th., " Entwicklung der Kontinente," p. 293. 



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



L.A. H 



