SOUTH AMERICAN—AFRICAN BRIDGE 27 
and South America require a connection from the South 
Upper American Continent and Africa. 
It was along this land bridge which the ancestors of the 
Notungulata traveled, and when in South America, due to 
their isolation, developed all the peculiarities of the group. 
This must have been not later than the latter part of the 
Cretaceous. 
Either this bridge remained until into the early Ter- 
tiary; so the Pyrotheria and [Tystricomorpha made their 
migration later, or these two groups did not reach the 
isolated Patagonian section until later than the first inva- 
sion. I am inclined to believe in the migration being at a 
later period. This bridge does not explain the presence of 
the edentates, for which there is every reason to believe 
that they developed in situ. The Marsupial invasion must 
have been from some other direction, or their presence in 
Africa has not yet been discovered. 
