82 THE GEOGRAPHY OF MAMMALS 



here southwards from North America, where their remains 

 (or those of closely allied species) have been likewise found in 

 the nearly contemporaneous formations of the United States. 



Moreover, it would seem that in these bygone days, 

 not only did the northern forms move southwards, but 

 that also some of the southern forms emigrated north- 

 wards. This is evidenced by the fauna of the so-called 

 " Equus-be&s" and " Megalonyx-beds " of a slightly later 

 date in the United States, which contain a composite 

 Mammal -fauna of northern forms mixed with forms 

 usually considered to be exclusively South American — 

 such as the gigantic armadillo-like Glyptodon, the Capy- 

 bara (Hydrochoerus), Toxodon, and others. 



Finally, in the age of the " Pampas " beds, the peculiar 

 South American Mammal-fauna seems to have reached 

 its culminating-point, and to have far exceeded that of 

 the present day both in number of species and in the 

 size of the individuals. This great increase in size, which 

 is, as a rule, accompanied by an extreme specialisation 

 of individual organs, seems to have had a fatal effect on 

 its possessors, as none of the larger Edentates or Toxo- 

 donts appear to have outlived the end of the pampas 

 formation. Along with most of the larger arrivals from 

 the north, such as Mastodon and Equus, they became 

 extinct. All the conclusions to be derived from this 

 much -abbreviated account of the extinct Mammals of 

 South America, confirm in a remarkable way the evidence 

 of the present fauna as to this history of the Neotropical 

 Region. Up to the last period of the Tertiary epoch, 

 South America was certainly isolated from the rest of the 

 world, and the connections with Australia and with Africa, 

 if they ever did exist, must have been previous to this 



