XI PALAEONTOLOGY AND EVOLUTION 373 



It is unfortunate that we have no knowledge of 

 the Miocene mammalian fauna of the Australian 

 and Austro-Columbian provinces ; but, seeing that 

 not a trace of a Platyrrhine Ape, of a Procyonine 

 Carnivore, of a characteristically South-American 

 Rodent, of a Sloth, an Armadillo, or an Ant-eater 

 has yet been found in Miocene deposits of Arc- 

 toggea, I cannot doubt that they already existed in 

 the Miocene Austro-Columbian province. 



Nor is it less probable that the characteristic 

 types of Australian Mammalia were already de 

 veloped in that region in Miocene times. 



But Austro-Columbia presents difficulties from 

 which Australia is free ; Camclidce and TapiridcB 

 are now indigenous in South America as they are 

 in Arctogasa ; and, among the Pliocene Austro- 

 Columbian mammals, the Arctogseal genera 

 Squus, Mastodon, and Machairodus are numbered. 

 Are these Postmiocene immigrants, or Proemio- 

 cene natives ? 



Still more perplexing are the strange and in 

 teresting forms Toxodon, Macrauchenia, Typo- 

 thcrium, and a new Anoplotherioid mammal 

 (Homalodotherium) which Dr. Cunningham sent 

 over to me some time ago from Patagonia. I con 

 fess I am strongly inclined to surmise that these 

 last, at any rate, are remnants of the popula 

 tion of Austro-Columbia before the Miocene 

 epoch, and were not derived from Arctogsea by 

 way of the north and east. 



