PAL^OMASTODON. 141 



other teeth (PI. XIII. fig. 1 b), which are regarded as being mm. 2, 3, 4, while on 

 the right only the two anterior ones are preserved. 



Mm. 2 consists of a large main cusp, laterally compressed and having a small 

 accessory cusp on its posterior edge. The cingulum is well developed on the front 

 of the tooth, where it forms a small cusp ; it is also present on the inner side, and 

 forms the edge of the prominent postero-internal angle of the tooth. 



Mm. 3 is a somewhat elongated tooth, wider behind than in front. Its anterior 

 angle is formed by a cusp of the cingulum. The rest of the tooth is bilophodont, 

 each transverse ridge consisting of a pointed outer cusp (scarcely at all worn in the 

 present specimen) and a rounded lower inner cusp (here much worn). There seems 

 also to have been a posterior cusp forming a sort of small talon and becoming 

 continuous in wear with the postero-internal main cusp. The cingulum is present on 

 the front of the tooth, at the inner end of the transverse valley, and on the outer side 

 of the posterior half of the tooth. 



Mm. 4 is trilophodont : the anterior ridge is composed of an outer sharper cusp 

 and a blunter inner one ; the other ridges are similar, except that the outer casp 

 is somewhat compressed from before backwards. The anterior angle of the tooth is 

 formed by a projection of the cingulum, which also appears at the inner ends of the 

 transverse valleys and on the hinder end and the posterior half of the outer side. 



Mandible (PI. XIV. fig. 3 ; text-figs. 48, 53, 54). — The mandible is very long and 

 must have projected a considerable distance in advance of the skull. 



The symphysis (PI. XIV. fig. 3, sym.) is greatly elongated and somewhat decurved : 

 its upper surface forms a spout-like groove bordered by the sharp edentulous alveolar 

 border; the groove is deepest in the middle, but with the rest of the symphysis 

 widens out towards the sockets of the incisors, the upper faces of which continue 

 the spout-like surface forwards. Ventrally the symphysis is deeply channelled in the 

 middle line between the alveoli of the incisors. 



Immediately beneath the third premolar (the first here present), which is situated 

 at a varying distance behind the posterior end of the symphysis in the different 

 species, the horizontal ramus deepens considerably ; it is flat on the inner face and 

 strongly convex from above downwards externally. The ascending ramus arises 

 from the outer face of the jaw, its anterior border being opposite the anterior lobe of 

 the last molar. This anterior border slopes slightly backwards and terminates above 

 in a very small backwardly curved coronoid process (text-figs. 53, 54, cor.). Behind 

 this the upper border of the ascending ramus is gently concave as far as the con- 

 dyle [cond.), which is rather higher than the coronoid process and is slightly convex 

 from side to side and very strongly so from before backwards. Prom it a broad 

 rounded thickening runs down to the posterior end of the alveolar border, and this ridge 

 is most strongly marked on the inner face, where immediately beneath it, and midway 

 between the end of the molar series and the hinder border of the jaw, there is the very 



