206 NEW YORK ZOOLOGICAL SOCIETY. 
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 
recently from Eurasia, but all have been here long enough to 
develop 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 
armadillos 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- 
