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 Hystricomorpha 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. 



