ON THE EXTINCT MAMMALS OF AUSTRALIA. 233 



the present fossil. The Diprotodon australis exceeded, however, both spe- 

 cies of Nototherium in size, so far as can be judged by the lower jaw and 

 teeth. 



The penultimate and last molar teeth very little exceed in any comparable 

 dimension those of the last described half-jaw, which from the length of the 

 fangs were as completely developed, and belonged therefore to an equally 

 mature animal ; but the depth of the jaw below the middle of the penultimate 

 molar in the present fossil is three inches three lines, and in the entire lialf- 

 jaw it is only two inches nine lines ; the thickest part of the jaw beneath the 

 same molar in that jaw is two inches three lines, but in the present fragment 

 it is only one inch eleven lines. In the entire half-jaw the external wall of 

 the alveolar process immediately swells out to form this thick part of the 

 ramus, but in the present fragment it maintains its thinness for an inch below 

 the margin of the socket, and the outer part of the jaw is slightly concave 

 here, before it begins to swell into and form the bold convexity which is con- 

 tinued to the thick inferior border of the jaw. This difference in the shape, 

 as well as the size of the jaw, bespeaks at least a specific distinction from the 

 jaw referred to Nototherium inerme. But a more marked distinctive character 

 in the present fossil is afforded by the relative position of the last molar tooth, 

 which is in advance of the origin or base of the corouoid process instead of 

 being internal to and hidden by that part when the jaw is viewed from the 

 outer side, as in the half-jaw. The outer surface of the anterior part of the 

 base of the coronoid appears, by a fracture there, to have projected outwards 

 further in the present specimen than in the half-jaw. 



The important marsupial character afforded by the inward bending of the 

 angle of the jaw is well-manifested by the present specimen, in which the angle 

 is entire ; it is thick and obtuse, and though slightly inflected in comparison 

 with the same part in the Wombat or Kangaroo, it bounds a well-marked 

 concavity which extends forwards to run parallel with the interspace between 

 the last and penultimate molars ; the regularity of the convex line extending 

 from the posterior part of the ascending ramus to the lower border of the 

 jaw is interrupted by a slightly produced obtuse prominence at the middle of 

 the inflected angle. The post-molar part of the alveolar process forms a 

 broad platform on the inner side of the base of the coronoid, and is defined 

 by a well-marked angle at its inner and posterior part, in which it resembles 

 both the lower jaw of the proboscidian Pachyderms and that of the Wombat. 

 The entry of the dental canal is situated as in the Diprotodon australis and 

 the Nototherium inerme. The coronoid process has the same extensive 

 antero-posterior origin, and the same thinness as in the half-jaw, but it is 

 rather more concave externally. Both the half-jaw and the present specimen 

 are from the alluvial or newer tertiary deposits in the bed of a tributary of 

 the Condamine river, west of Moreton Bay, Australia ; they are mineralized, 

 but of a deeper ferruginous colour than the fossils of the Diprotodon. 



An astragalus of the same colour and mineral condition, and from the same 

 locality as the preceding specimens, belongs also more probably to the Noto- 

 therium than to the Diprotodon, on account of its somewhat smaller size than 

 the calcaneum above described. The peculiarities of this astragalus will 



be obvious to the Comparative Anatomist from the following description : 



It is a broad, subdepressed and subtriangular bone, the angles being rounded 

 off, especially the anterior one ; the upper or tibial surface is quadrate, con- 

 cave from side to side, in a less degree convex from before backward ; a ridge 

 extending in this direction divides the tibial from the fibular surface, which 

 slopes outwards at a very open angle and maintains a nearly horizontal aspect, 

 presenting an oblong trochlea for the support of the fibula, shallower, and 



