PALiEOJVIASTODON. 
141 
otlier teetli (PL XIII. fig. 1 b), which arc regarded as being mm. 2, 3, 4, while on 
the right only the two anterior ones are ])reserved. 
j\Im. 2 consists of a large main cus]), laterally comy)ressed and having a small 
accessory ensp on its ])osterior edge. The cingnlnra 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 ])rominent 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 cusp 
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 tovvards 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. From 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 
