ON THE EXTINCT MAMMALS OF AUSTRALIA. 231 



elusions are deducible from the portions of jaw above described, which cor- 

 respond in proportional size, mineralized condition, locality and stratum, with 

 the present calcaneum, it is highly probable that they all belong to the Di- 

 protodon australis, a species whose affinities to the Wombat were perceived 

 by the characters of the single tusk and fragment of jaw first transmitted 

 from the caves of Wellington Valley. 



Genus Nototherium. 



Species 1, N. iiierme. 



I next proceed to notice a second small but instructive series of fossils, in- 

 cluding portions of lower jaws, which, by the total absence of incisors, indi- 

 cate a distinct genus of pachydermoid Mammals, with the same kind and 

 amount of evidence of its marsupial affinities : the principal fossil is the 

 almost entire right ramus of the lower jaw. 



The dentition in this jaw consists of molar teeth exclusively, four in num- 

 ber, which increase in size as they approach the posterior part of the series : 

 a small portion of the anterior end of the symphysis is broken away, but 

 there is no trace there of the socket of any tooth, and it is too contracted to 

 have supported any tusk or defensive incisor. The length of the jaw is eleven 

 inches : the molar series, which commences one inch in advance of the pos- 

 terior border of the symphysis, is six inches in extent: each tooth is im- 

 planted by two strong and long conical fangs, the hindermost being the 

 largest, and both being longitudinally grooved upon the side turned to each 

 other. The first tooth is wanting, and the crowns of the rest are broken 

 away : the base of the third remains, and gives an indication of a middle 

 transverse valley, which most probably separated two transverse eminences. 

 This jaw resembles that of the proboscidian Pachyderms in the shortness of 

 the horizontal ramus ; and of the Elephant more particularly, in the rounding 

 off of the angle, and in the convex curvature of the lower border of the jaw 

 from the condyle to the symphysis, and also in the smaller vertical diameter 

 of the symphysis, and the more pointed form of that part. It resembles the 

 jaw of the Elephant in the form, extent and position of the base of the coro- 

 noid process, but it differs from the Elephant in the concavity on the inner 

 side of the posterior half of the ramus of the jaw, which is formed by an in- 

 ward inflection of the angle : this concavity extends forwards beneath the 

 sockets of the two last molar teeth. It differs from the lower jaw of the Ele- 

 phant in the greater flatness of the outer part of the angle of the jaw, in 

 which respect it more resembles the Mastodon. In the extent of the angle 

 of the jaw it is intermediate between the Mastodon and Elephant. It differs 

 from both in the inward bending of that angle, which is remarkable for the 

 great longitudinal extent along which the inflection takes place : most of the 

 inflected angle has been broken away, but enough remains to demonstrate a 

 most instructive and interesting coi'respondence between the present fossil 

 and the characteristically modified lower jaw in the marsupial animals. In 

 pursuing the comparison of the Australian pachydermal fossil with the Mas- 

 todon and Elephant, we may next observe that the alveolar process on the 

 inner side of the base of the coronoid, behind the last molar, is as well deve- 

 loped as in the Mastodon : a similar angular production of this part exists, 

 however, in the Wombat and Kangaroo. The vertical extent of the outer 

 concavity of the coronoid process is greater in the Australian fossil than in 

 the jaw of the Mastodon, and is less clearly defined below. The dental canal 

 commences by a foramen penetrating the ridge which leads from the condyle 

 to the post-molar process, and apparently just below the condyle, as in the 

 Elephant, but it is relatively much smaller : it does not communicate with 



