178 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



of the upper jaw with upper molars, of the so-called Zygomatiirus, 

 the British Museum possesses a portion of the right side of the 

 upper jaw with three molars of the Nototherium (Pl.IX.figs.4 and 5), 

 identical, at least in size, general configuration, and in the character 

 of the enamelled surface, with the teeth in the lower jaw of that 

 genus : the same collection also possesses an almost entire lower jaw 

 of the Nototherium Mitchelli (Plate IX. fig. 1) from the forma- 

 tions cut through by the Condamine Eiver, in the plains west of 

 Moreton Bay. 



I propose first to describe the ramus of the lower jaw of the 

 Nototherium inerme (Plate IX. fig. 3), afterwards the almost entire 

 mandible of the Nototherium Mitchelli (ib. figs. 1 and 2), and finally 

 to point out the resemblances between the dentition of these jaws 

 and that of the fragment of the upper jaw, and the casts of the fossil 

 bilophodont skull, previously described. 



The specimen of Nototherium inerme (fig. 3) transmitted by Mr. 

 Hughes to the Museum of Natural History at Worcester, from the 

 tertiary deposits forming the bed of the Condamine, consists of the 

 right ramus*, and back part of the symphysis of the mandible, but 

 with the condyloid, coronoid, and angular processes, and the fore 

 part of the symphysis broken away. 



The ramus is short, very thick in proportion to its length and 

 especially its depth, convex on the outer side of the dentigerous 

 part, slightly convex vertically on the inner side, and with the 

 lower border describing a convex curve from the condyle to the sym- 

 physis, which seems to have been interrupted but slightly, if at all, 

 by any projecting angle ; for although the angle has been broken off, 

 it has plainly been bent inward. 



The fractured base of the condyloid process presents a triangular 

 form, two inches in its longest diameter : the outer and most obtuse 

 angle forms the hind part of the ridges bounding inferiorlj^ the ex- 

 ternal coronoid fossa ; the upper and most produced angle forms the 

 back part of the base of the coronoid process ; the inner and lower 

 angle forms the same part of the angular process. 



The outer part of the ascending ramus is divided into two facettes 

 by the first-named thick ridge or rising of the bone, which extends 

 from the outer side of the condyle obhquely downwards and forwards 

 with a curve concave towards the external coronoid fossa. 



The base of the coronoid process begins anteriorly one inch ex- 

 ternal to the socket of the last molar tooth, the hinder half of which 

 tooth would be concealed by the process in a side-viewf. The frac- 

 tured base of the process extends to the condyle, with a slight curve 

 concave outwards ; it is about half an inch thick at the beginning, 

 but soon diminishes to 3 lines and then to 2 lines in thickness, the 

 plate of bone being thinned off, as it were, by the depressions for 

 muscular insertion on both its outer and inner sides : it is 3 ^ inches 

 in extent to where it joins the fractured base of the condyloid pro- 



* Drawn on the plate without being reversed. 



' t This is one of the specific characters of Nofothermm inerme, given in the 

 " Report," p. 12, and illustrated in pi. 3. figs. 1, 4. 



