SUCCESSIVE MAMMALIAN FAUNAS 215 



in the southern continent now. Several species of fmastodons 

 have been found in Brazil, Argentina, Bolivia and elsewhere, 

 but none of the true elephants. Why the fmastodons were 

 able to make their way into South America, while the elephants 

 were not, is one of the puzzling questions of mammalian dis- 

 tribution to which no answer can be given. 



All the preceding types of hoofed animals, the horses, 

 tapirs, peccaries, llamas, deer, antelopes and fmastodons were 

 migrants from the north, and four of these, tapirs, peccaries, 

 llamas and deer, were able to gain a permanent footing in 

 South America and are more or less abundant there to-day, 

 while the horses, antelopes and fmastodons failed to do so 

 and died out. In addition to these, there were the indigenous 

 types, which are now extinct and have never been found out- 

 side of the Neotropical region. An extremely peculiar creature, 

 \Macrauchenia, was the last surviving member of an order, the 

 fLitopterna, which for ages played a very important role in 

 South America. ]Macrauchenia was a large animal, somewhat 

 larger and of much heavier build than a camel, to which it 

 had a considerable, though entirely superficial, resemblance. 

 The head was relatively small and must have had quite a long 

 proboscis ; the neck was very long, suggesting that the animal 

 browsed upon trees, which is also indicated by the character 

 of the teeth ; the legs were long and stout, the feet short and 

 each provided with three toes. Another curious creature was 

 jTypothermm, from which is named the group of the fTypo- 

 theria, which some authorities regard as a suborder, while 

 others assign to it a full ordinal rank. 



The fTypotheres throughout the Tertiary period were 

 among the most abundant and characteristic of the South 

 American hoofed animals, and the genus '\Typotherium was the 

 last of a very long series and was an animal of moderate size, 

 with chisel-shaped incisor teeth so like those of the rodents 

 that the genus was long referred to that order. Finally, we 

 have "fToxodon, type of the order fToxodontia, a ponderous 



