HISTOEY OP SOUTH AMERICA 337 



water since the close of the Mesozoic Era. The testimony is 

 of a threefold character. It is founded on our knowledge of 

 geology, of palaeontology, and of the geographical distribu- 

 tion of living animals and plants. Eichness, as Dr. Wallace' 

 observed, combined with isolation, is the predominant feature 

 of neotropical zoology. Nevertheless, he thinks that early 

 during the Tertiary Era, the zoological differences between 

 the Nearctic and Neotropical, that is to say, between the North' 

 and South American regions, were probably even more radical 

 than they are now. South America, he argues, was then a 

 huge island or group of islands — a kind of Australia of the 

 New World — chiefly inhabited by the imperfectly organised 

 group of edentate mammals. Dr. Wallace* believes, more- 

 over, that there must have been one or more ancient lan,d 

 connections between the two continents, perhaps in Eocene 

 or Miocene times, admitting ancestral types of monkeys and 

 the members of the camel-tribe (Llamas) from the north to 

 South America. 



Dr. Wallace's opinions, expressed thirty-five years ago, 

 were founded entirely on the distribution of living animals. 

 Rapid strides have been made since that time in our knoiw;- 

 ledge of the fauna of South America. The geology of certain 

 districts is being worked out. Botanists have made great 

 progress in mapping out the distribution of plants, while the 

 most astonishing discoveries have been disclosed principally 

 among the past inliabitants of the continent. Thus we are 

 now in a very different position from that of Wallace, when 

 he pronounced upon the physical changes of South America 

 during the past, on the strength of his zoological know- 

 ledge. 



We are particularly indebted to Dr. von Ihering's re- 

 searches on the fauna and flora of South America, which he 

 conducted during many years of devoted labour, that our in- 

 formation on the main features of distribution has advanced 

 so rapidly. During his long residence in southern Brazil he 

 collected, and is still collecting, data bearing principally ort 

 the question of the geological history of the continent ; and 

 since his scattered papers have recently been reprinted in' 



* Wallace, A. E., " Distribution of Animals,'' II., p. 58. 

 L.A. Z 



