PAL^OMASTODON. 21 



transverse ridges, these teeth being subjected to two distinct 

 influences, namely, the tendency to the reduction in the 

 front of the series and the tendency to become more like the 

 molars at the back. The three molars themselves show a 

 distinct advance, the crown of each consisting of three transverse 

 ridges, each ridge composed primarily of t\\ o main cusps which 

 may, however, show small traces of sub-division into secondary 

 cusps. 



The mandible (figs. 9 & 13 A) differs from that of Moeri- 

 therium in the much greater prolongation of the spout-like 

 anterior portion ; this now projects a considerable distance 

 in front of the skull and is prolonged still further forward by 

 the single remaining (second) pair of incisor teeth, which meet 

 in the middle line and from a sort of shovel-shaped extension ; 

 the edges are worn both 011 the upper and lower surface, so that 

 these teeth were probably used for grubbing about in the ground 

 to procure food, and the upper surface must have been further 

 worn by working against the lower surface of the trunk or 

 elongated upper lip. 



There are only two premolars in the lower jaw, the anterior 

 of the three milk-molars (figs. 9 & 13 A) falling out without 

 being replaced from below ; the molars are three in number, 

 the two anterior with three transverse ridges, the third some- 

 times having in addition a small heel (fig. 10 B). It should be 

 noticed that in the full-grown animal all the molars and pre- 

 molars are in position and use at the same time ; it will be seen 

 that in the later forms of elephant-ancestors this is not so. 



The skeleton, so far as known, is almost exactly like that of 

 a small elephant, the only important differences being that the 

 neck is longer and the limbs most likely less massive. The animal, 

 as a whole (fig. 11), must have been very like a small elephant, 

 but would be distinguishable by the longer head and neck, and 

 by the fact that instead of possessing a flexible trunk it had a 

 long snout, the lower portion consisting of the elongated lower 

 jaw,, the upper without bony support and probably extending 

 beyond the lower ; the projecting portion most likely was more 

 or less flexible and capable of seizing objects, and was the 

 beginning of the prehensile trunk. 



