394 
ORIGIN OF LIFE IN AMERICA 
westward. During part of (Secondary times eastern Brazil 
was most likely united by land with West Africa. During the 
Cretaceous age already, the southern Atlantic rapidly advanced 
northward, invading eastern Brazil, so that the land bridge 
then joined only northern South America and a small tract 
of West Africa. In Eocene times the southern trans-Atlantic 
land connection had ceased to exist, yet the South American 
continent must have extended still far eastward of its present 
coast-line. Eastern Brazil continued to receive new additions 
to its fauna from the northern States of South America while 
its area extended gradually westward. When Brazil finally 
became joined to Argentina a faunistic interchange took 
place, although Brazil and Chile remain to the present day 
two fundamentally distinct countries. 
