EIGHTH ANNUAL REPORT. 29 



To sum up the contents of the preceding pages we find that we 

 have: 



First: The Puerco radiation (in Europe also in part) ; 



Second: The Wasatch or Lower Eocene radiation (in Europe 

 also in part). 



In each of these two radiations we have three elements: 



a. A fauna found both in America and in Europe ; 



b. An independent American fauna; 



c. An independent Eurasiatic fauna. 



Third : A portion of the Second or Wasatch American fauna, 

 by migration into Europe. 



Fourth : A portion of the Second or Lower Eocene Eurasiatic 

 fauna, by migration into America. 



In Miocene times there also appears an African fauna, a large 

 portion of which enters Europe and Asia, sending into North and 

 South America mastodons and into North America only, mam- 

 moths and modified Bovidae. In Pliocene times North America 

 receives a South American fauna. 



This completes our review of the important mammals of North 

 America. 



We find that the great majority of our large animals came re- 

 cently from Eurasia, but all have been here long enough to de- 

 velop characters of specific rank. 



There is also a native element, which seems to have survived 

 the devastation of the glaciers, including the prong-horn, the 

 American deer, the peccaries, the raccoons and the opossums. 



A small South American element, consisting chiefly of the ar- 

 madillos and the porcupines, of considerable antiquity, can also 

 be traced. 



The element of recent arrivals is naturally strongest in the 

 North, and in the Arctic itself we find certain species, like the 

 white bear and the arctic fox, which are circumpolar in their 

 distribution. 



In the South the native element and the South American types 

 become more and more prominent as we proceed through the 

 United States and Mexico southward, until at last the face of 

 nature changes, and we find ourselves in the tropics, amid the 

 strange fauna of South America. 



The writer desires to express his deep sense of appreciation of the 

 courtesy and aid in the preparation of the above paper, of Prof. Henry 

 Fairfield Osborn and of Dr. W. D. Matthew, both for their special knowl- 



