358 
ORIGIN OF LIFE IN AMERICA 
received its quota of European emigrants, they found suitable 
accommodation on the newly formed land of north-western 
South America. The mid-Atlantic land bridge now ceased 
to exist, and far-reaching geographical changes super¬ 
vened almost everywhere. Owing possibly to the extensive 
subsidences in the Pacific Ocean, the land that I assume to 
have occupied part of the eastern Pacific, was gradually re¬ 
duced in size. But, being no longer tenanted by the more 
vigorous and more advanced European types, South American 
forms now commenced to occupy this land, thus first reaching 
the Antilles and then North America as it again became fully 
connected with the western land. Central America in its pre¬ 
sent shape had not yet come into existence. Not long ago it 
was thought that the Central American isthmus must have 
been first utilised as a highway at the beginning of the Plio¬ 
cene Period, and that then the great edentates began to pour 
into North America. Now the surprising evidence has come 
to hand that true edentates of the Megalonyx type occur in the 
Middle Miocene Mascall beds of Oregon. Dr. Matthew writes 
to inform me that the Megalonyx remains only doubtfully 
belong to this horizon. Professor Osborn,* on the other hand, 
believes in the discovery, and expresses the opinion that it 
tells in favour of my theory of the former existence of a 
western land connecting North and South America inde¬ 
pendently of Central America. Still, he points out that it is 
inconsistent with the fact that oilier animals did not pass 
south or north. 
Let us examine some of the other new arrivals in North 
America in Miocene times, and endeavour to trace their geo¬ 
logical history. One of the most noteworthy of these is the 
first appearance in North America of elephants (Mastodon). 
Since Dr. Andrews’ f surprising discoveries in northern 
Africa were published, Africa is generally looked upon as the 
original home of elephants, the earliest form being Moeri- 
therium, from which later on Palaeomastodon and its more 
modern relations arose. The first of the latter was the Mas- 
* Osborn, II. F., “ Age of Mammals,” pp. 289—292. 
f Andrews, C. W., “Tertiary Vertebrates of the Fayum,” pp. xvi—■ 
xviii. 
