436 LAND MAMMALS IN THE WESTERN HEMISPHERE 



the generic peculiarities were to be found in the teeth and skull. 

 There were no superior tusks, all the upper incisors and canines 

 being lost, but there was a pair of large lower tusks, which 

 were directed downward, with a strong backward curvature. 

 The dental formula then was : i^, c^, 79 1, rwf, X 2 = 22. The 

 grinding teeth were relatively quite small and had, except the 

 first molar, two transverse crests, giving a pattern singularly 

 like that seen in the tapirs. The skull was remarkably long, 

 low and flat, and no doubt these animals had a proboscis of 

 some sort. That the fdinotheres were derived from the same 

 ancestral stock as the fmastodons and elephants is perfectly 

 obvious and is not questioned by any one, but it is not yet 

 possible to trace the connection. 



The proboscideans were late immigrants into South 

 America, being known there only in the Pleistocene and late 

 Pliocene times, and only the fmastodons entered the southern 

 continent, where they gave rise to several peculiar local species 

 in Argentina, Bolivia, Chili and Brazil; one of these {"f Mas- 

 todon andium) had a deposit of cement on the crowns of the 

 grinding teeth. Why the elephants, which extended to the 

 northern border of the Neotropical region, should have failed 

 to reach South America and maintain themselves there, is but 

 one of many similar questions to which no assured answer can 

 be given. 



The evolution of the Proboscidea was, in a certain sense, 

 very similar to that of the foreodont family (p. 381) among the 

 Artiodactyla, in that the developmental changes affected 

 chiefly the dentition and the skull, the skeleton of the body 

 and limbs having very early acquired a character which was 

 afterward but little modified. Were the skull and teeth of the 

 lower Miocene '\Gomphotherium not known, we should hardly 

 hesitate to refer the skeleton to the genus Elephas, and even 

 in the Oligocene ^Paloeomastodon all the bones of the skeleton, 

 other than the skull, were characteristically and unmistakably 

 proboscidean. On the other hand, the transformations of the 



