RANGE OP FOSSIL ELEPHANTS 
409 
tied, from all available data, that North and South America 
became joined at the commencement of the Pliocene Period. 
It was supposed that the advance of northern types, such as 
the mastodon and hosts of others, towards the southern con¬ 
tinent must have coincided with the opening up of the new 
land of Central America. The occurrence of edentate remains 
in North American Miocene deposits upsets this theory, 
because, if mammals were able to reach North America from 
the south during the Miocene Period, northern species must 
have had equal facilities for invading South America at this 
time. If there is geological evidence that Central America was 
not available as a safe land bridge between North and South 
America in Miocene times, some other land connection 
must have united the two continents. When I advanced the 
theory of the former existence of a Pacific land bridge between 
North and South America, westward of Central America,* I 
was unaware of Professor Sinclair’s interesting discovery 
among the Mascall beds of Oregon. My theory was largely 
founded on zoogeographical data—on curious instances of 
discontinuous distribution of ancient groups in North and 
South America. Professor Osborn f regards my theory as 
inconsistent with the fact that the Pacific land bridge should 
only have been used by these gravigrade sloths. If such a 
land connection really existed why was it not more exten¬ 
sively used ? I think it was used by other animals, such as the 
mastodons and the ancestors of the llamas to pass southward, 
and by the ancestors of the North American tree porcupines 
in entering North America. 
Since I wrote my essay on the problem of a former land 
connection, other than the Central American one, between 
North and South America, I have had opportunities of study¬ 
ing the subject more at my leisure. I find that the affinity 
existing between south-western North America and the 
extreme south of South America among some of the more 
ancient groups of animals is greater than I thought. Let 
us examine this curious relationship between the two 
widely separated faunas a little more closely. I explained 
* Scharff, B. F., “ Early Tertiary Land-connection.” 
t Osborn, H. F., “Age of Mammals,” p. 292. 
