112 LAND MAMMALS IN THE WESTERN HEMISPHERE 



ferences among the animals. This inference is confirmed by 

 the discovery of a Bridger genus, very fragmentary but identi- 

 fiable, in the marine Eocene of New Jersey. 



South America. — No Eocene rocks, marine or continental, 

 are known in the West Indies or Central America, but the latter 

 region has been so imperfectly explored that no great impor- 

 tance can be attached to this fact. North and South America 

 were separated completely, as is proved by the entire dis- 

 similarity of their mammalian faunas, but the position of the 

 transverse sea or strait cannot be determined. There is much 

 reason to believe that the Greater Antilles were connected 

 into a single large land, which has been called "Antillia" 

 and may have been joined to the mainland of Central America. 

 Certain marine rocks in Patagonia and Chili have been re- 

 ferred to the Eocene by South American geologists, but the 

 reference is almost certainly erroneous, the rocks in question 

 being much more probably Miocene. The Andes, probably 

 throughout their length and certainly in their southern half, 

 stood at a much lower level than they do now, and, no doubt, 

 were rising, either slowly and steadily, or periodically and more 

 rapidly, throughout the whole Tertiary period. At all events, 

 their present height in the south is due to movements in the 

 Pliocene or later. Continental deposits of Eocene date have 

 been discovered only in northern Patagonia (Casa Mayor) 

 where they occupy depressions in the worn and eroded sur- 

 faces of the Cretaceous rocks; the mode of their formation 

 has not been carefully studied. 



There is great uncertainty as to the status of the land- 

 bridge which, it is beheved, in the Cretaceous period connected 

 South America with Africa. Some of the evidence goes to 

 show that the connection persisted throughout the Eocene 

 epoch, but the testimony is that of fragmentary and therefore 

 imperfectly understood fossils and is far from being unequivocal. 

 The connection with Antarctica probably continued. 



