6$ W. D. Matthew — Mammalian Migrations 



Akt. VI. — Mammalian Migrations between .Europe and 

 North America ; by W. D. Matthew."- 



Depeket advocates a more continuous interchange of faunse 

 during the Tertiary between Europe and North America than 

 we of the American Museum of Natural History are disposed 

 to admit. But Dot so much more as one might infer. He 

 pointed out evidences for interchange in Puerco and Torrejon, 

 Wasatch. Wind River, then a break, then in Lower and Middle 

 Oligocene and, I think, in Middle and Upper Miocene, in Plio- 

 cene and Pleistocene. This is mot very far from Osborn's view. 

 Personally, I think there is no good evidence for Wind River 

 connection, for Middle Oligocene or for Upper Eocene con- 

 nection. To me the evidence appears thus :— In the Basal 

 Eocene the faunae were closely related, the results presumably 

 of an extensive migration at the end of the Cretaceous. In the 

 Wasatch a large immigrant fauna appears in both countries 

 which I regard provisionally as of Asiatic origin ; then inde- 

 pendent development till the end of the Eocene. At the begin- 

 ning of the Oligocene here, and in the Upper Eocene of Europe 

 and North America, there appears a large new immigrant fauna, 

 which may also be referred to Asiatic origin. Then as far as 

 I can see, there was independent development until the Middle 

 Miocene, when several important, modernized types appear in 

 this country, which had been appearing in Europe in the Oligo- 

 cene, Lower and Middle Miocene. The fauna of the Upper 

 Miocene in America seems to me mainly or entirely of autoch- 

 thonic origin, but in the Pliocene a further interchange takes 

 place, again in the Lower Pleistocene, and in the late Pleisto- 

 cene, between Old and New world. 



This means practically continuous interchange in the late 

 Tertiary, more interrupted in the earl} 7 part. As for the route, 

 as I recall Deperet's remarks, he spoke of that across Bering 

 straits as the most probable, and regretted that our lack of 

 knowledge of the Tertiary land formations of Asia prevented 

 us from proving or disproving this route. 



I admit quite freely that Deperet's conclusions follow from 

 his data, on the face of the evidence. But when the returns 

 are as fragmentary as in the European Eocene, I think we have 

 a right to go behind them. His assumption is that because a 



* This important statement is in response to a letter asking for farther 

 information in regard to the view expressed by Deperet, at the recent Seventh 

 International Zoological Congress, that there was constant intermigration of 

 mammals between Europe and America. The same authority further believes 

 that the great similarities between the faunae of Europe and America can 

 not be explained on the basis of considerable parallel development. — C. 

 Schuchert. 



