PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
65 
marked in the adult than in the young animals, becoming more conspicuous in 
Biprotodon as the incisive tusk acquires its adult proportions. 
In all the Nototherian mandibles the lower border is inflected at two parts; the one 
in the horizontal portion, the other in the ascending portion, or “ ramus.” It may well 
be that this character, which is not present in Kangaroos and Wombats, may be pre- 
sented by Biprotodon , when a perfect mandible of that animal is obtained ; but it the 
fore part of the inflected border shown in the subject of Plate xlii. fig. 2 (Phil. Trans. 
1870) be the beginning of an anterior inflection divided by a non-infiected tract from 
the posterior inflection, which represents the inflected angle in Macropus and Phasco- 
lomys , such beginning is more posterior in position, more nearly where the angular 
inflection begins in Nototherium. In the adult jaw of N. Victories (Plate VII.) and in 
the immature one of N. Mitchelli (Plate VI.) the whole extent of the anterior inflection 
( d ) is shown ; only, in the adult specimen, the free border has suffered. 
The orifice of the dental canal is raised to a level above that of the summits of the 
last molars in Biprotodon. The largest of the species of Nototherium differs little in 
this respect ; but in N Victories and N. inerme the orifice is brought down to, or near 
to the level of the alveolar outlets. In the smaller existing herbivorous Marsupials it 
is placed still lower, being hidden in an excavation which does not exist in the extinct 
pouched herbivorous giants. 
Of the position of the condyle we can speak only as it is indicated in Nototherium 
Victorias. Here it is raised high above the level of the molar series, as in all herbivorous 
Marsupials, but not so much raised relatively as in Biprotodon. 
In the curve by which the coronoid process advances and rises from the fore part of 
the neck of the condyle, Nototherium resembles Phciscolomys more than it does Macropus , 
in which the process rises in almost a straight line obliquely forward to its pointed apex. 
§ 4. Bentition. — The dental formula of Nototherium , as of Biprotodon , is i c ~, 
m 28. The homologies of the molars with those of diphyodont Mammals are 
given by the symbols d 3, d 4, m i, m 2 , m 3 , by which those teeth in the present paper 
will be signified as they range from before backward *. 
The upper incisors, i 1 , i 2 , i 3 (Plate II. fig. 1, Plate III. fig. 3), follow one another in 
the same direction in each premaxillary, the foremost being the largest and the sole pair 
visible in a front view (Plate I. fig. 2). The right and left series run nearly parallel, 
slightly converging posteriorly ; the greater interval between the right and left incisors 
of the second and third pairs is due to their smaller size, and their outer surface ranging 
with that of the larger exterior pair (Plate II. fig. 3, 22 *). In the old Nototherium Mit- 
chelli the first incisor does not project beyond an inch from the socket, the crown being 
* In my Memoir on Nototherium (Quarterly Journal of the Geological Society, vol. xv. 1859), I state, in 
regard to these molars, that “ the first appears to be a premolar and the rest true molars” (p. 171). I am now 
able to adduce [Plate YI. fig. 5] evidence that the first tooth is the homologue of d 3 in Macropus, and has no 
vertical successor =p 3. 
MDCCCLXXII. K 
