336 TROPICAL NATURE, AND OTHER ESSAYS. 



migration took place at the end of the Pliocene or 

 beginning of the Post-Pliocene epoch, owing to some 

 specially favourable conditions, but that they rapidly 

 disappeared, having left no survivors. We must, how- 

 ever, study the past history of South America in order 

 to ascertain how far it has been isolated from or con- 

 nected with the northern continent. 



Abundant remains of the Post-Pliocene epoch from 

 Brazilian caves show us that the fauna of South America 

 which immediately preceded that now existing had the 

 same general characteristics, but was much richer in 

 large mammalia and probably in many other forms of 

 life. Edentata formed the most prominent feature ; but 

 instead of the existing sloths, armadillos, and ant-eaters, 

 there were an immense variety of these animals, some of 

 living genera, others altogether different, and many of 

 them of enormous size. There were armadillos as large 

 as the rhinoceros, while the megatherium and several 

 other genera of extinct sloths were of elephantine 

 bulk. The peculiar families of South American rodents 

 cavies, spiny-rats, and chinchillas were represented by 

 other species and genera, some of large size ; and the 

 same may be said of the monkeys, bats, and carnivora. 

 Among Ungulata, however, we find, in addition to the 

 living tapirs, llamas, peccaries, and deer, several species 

 of horse and antelope, as well as a mastodon, all three 

 forms due probably to recent immigration from the 

 northern continent. 



Further south, in Bolivia, the Pampas, and Patagonia, 

 we also find abundant fossil remains, probably a little 

 older than the cave fauna of Brazil, and usually referred 

 to the newer part of the Pliocene period. The same 



