432 LAND MAMMALS IN THE WESTERN HEMISPHERE 



form and so worn as to show that they were regularly employed 

 in cropping and browsing. The skull was low and broad and 

 the symphysis of the lower jaw was greatly prolonged to carry 

 the tusks. 



A very important fact concerning these early fmastodons 

 is that they had the normal method of tooth-succession, per- 

 manent premolars forming beneath (in the lower jaw, above 

 in the upper) the milk-teeth and pushing them out at maturity. 



Of the middle Miocene proboscideans not much is known 

 beyond the mere fact of their presence in North America 

 at that time and indeed little of the skeleton, other than the 

 skull, has yet been found in the American Miocene ; but well- 

 nigh complete skeletons have been obtained from the middle 

 Miocene of Europe, and these bring out the surprising fact that 

 the body and limbs of these species did not differ in any note- 

 worthy manner from those of the existing elephants ; the 

 modern skeletal structure of these animals had been attained 

 at a time when the dentition and skull were still in a far less 

 advanced stage of development. In size, however, there was 

 a decided difference, the species of the American Miocene 

 rarely attaining a height of six feet. 



Proboscidea have been reported from the lower Miocene 

 of the Great Plains, but the material is insufficient for a defin- 

 itive judgment. There is no doubt as to their presence in 

 Europe at that time, but in neither continent can the history 

 be traced any farther and we must turn to Africa for a back- 

 ward continuation of the story. In the lower Oligocene of 

 the Fayum, southwest of Cairo in Egypt, occurs the highly 

 interesting genus '\Pal(Eom,astodon, which was much more 

 primitive than any of the genera described above, though it 

 was an unmistakable member of the order and even of the 

 family Elephantidse. The dentition was already much re- 

 duced, giving the formula : i\, c^, p^, m f . The upper tusks 

 were short, compressed, directed downward, and slightly diver- 

 gent, and had a broad band of enamel on the outer side ; the 



