330 Prof. Owen on a new species of Dinotherium, 



In the genus Mastodon the antero-posterior diameter of the 

 molars and the number of the transverse eminences or pairs 

 of tubercles on their grinding surface increase, as the teeth 

 are placed further back in the jaw : thus, in the M. yiganteus, 

 whose teeth bear most resemblance to the Dinothenan type, 

 the first and second molars have two transverse ridges, the 

 third and fourth have three ridges, and the last molar has 

 four or five ridges. In the portion of jaw from the Darhng 

 Dow^ns, figured by Sir Thomas Mitchell, which contains the 

 third and fourth molars, the former (fig. 1, b) has three transverse 

 ridges, and is of greater antero-posterior extent than the fourth 

 molar, which has only two transverse ridges. In the shape 

 as well as proportions of the teeth, the Australian fossd agrees 

 with the different species of Dinotherium that have been dis- 

 covered in the Miocene of Europe. The Australian species 

 is somewhat less than the Dinotherium medium of Kaup. The 



Fig. 2. 





Grinding surface of third and fourth molars. 

 Dinotherium Juslrale : one-third nat. size. 



degree of correspondence, in both size and shape, of the teeth 

 in the jaw figured by Sir Thos. Mitchell with the portion of 

 the molar represented at p. 9, figs. 2 and 3, would indicate the 

 latter to be part of an anterior molar of the same species of 

 Dinotherium, if not of the same individual. The traces in the 

 femur of the unobliterated junction of the condyloid epiphysis 

 with the shaft of the bone indicated it to have belonged to a 

 young though nearly full-grown animal, and it would seem 

 that the last molar of the lower jaw had not come into place, 

 for in the figure of the portion of the jaw, the cavity which 

 contained it appears to be indicated at a, fig. 1. The sum- 

 mits of the ridges of the fourth molar are represented sharp 

 and unworn, like those of a tooth that had been recently ac- 

 quired. 



We may thus assume, with a high degree of probability, 

 that the portions of jaw, femur and teeth associated together. 



