68 
PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
of the summits of the two lobes is downward and a little forward ; they run across the 
tooth rather more obliquely than in Diprotodon (Phil. Trans. 1870, Plate xxxvii. fig. 2, 
d 4 ), but with a similar curve of the apical ridge slightly concave backward. The less 
exposed enamel toward the bottom of the valley and near the basal ridges is punctate ; 
but generally the enamel is smoother and more polished than in Diprotodon. This 
molar, like the rest of the upper ones, is implanted by two transversely disposed anterior 
roots (Plate IX. fig. 8), and one long transversely extended posterior root. 
The third molar (Plate IX. figs. 3 & 4, m 1 ) has its ridges extended rather less obliquely 
than in d 4 , but more so than in m 1 of Diprotodon. The antero-posterior diameter is 
1 inch 4 lines ; the transverse diameter 1 inch 3 lines. As the lobes are more entire 
they show better the curve of their summits, concave backward. The thicker anterior 
basal ridge ( f) is continued at both ends upon the corresponding borders of the anterior 
lobe. The posterior basal ridge (g) is continued internally to the apex of the posterior 
lobe, gradually subsiding ; externally it curves upon the end of the lobe, and subsides 
halfway to the summit. 
The fourth molar (Plate IX. figs. 3 & 4, m 2 ) shows a diminution of breadth of the 
hind lobe in a greater degree than the corresponding tooth does in Diprotodon ; its fore- 
and-aft extent is 1 inch 8 lines. The transverse breadth of the front lobe is, in the old 
male (fig. 7), 1 inch 7 lines; in the subject of fig. 4, 1 inch G lines; that of the hind 
lobe is 1 inch 5 lines. The inner end of each lobe is made thicker by a backward 
expansion, rather more marked in m 2 than in m 1 . 
I 11 the last molar (Plate IX. figs. 3 & 4, in 3) the slightly abraded summits of the 
lobes show the more vertical or steeper slope of their fore side, which is convex 
transversely ; also the transverse concavity of the hind side, due to the seeming backward 
bend, with thickening, of the outer and inner borders, and the curving slope of the hind 
part of the lobes, which gives them in profile a slight bend forward (fig. 3 , m 3) as in 
Diprotodon. 
The fore-and-aft extent of this tooth is 1 inch 8 lines ; the breadth of the front lobe 
is 1 inch 7 lines ; that of the hind lobe is 1 inch 3 lines ; it contracts more rapidly 
to its summit than in Diprotodon. The posterior root of m 3 is slightly impressed 
lengthwise at its back part, and deeply so at its fore part. 
The origin of the outstanding zygomatic process of the maxillary terminates poste- 
riorly opposite, or on a vertical parallel with, the interspace between the third and fourth 
molars. In one large old Notothere (Plate IX. fig. 6) it extends, as before observed, 
a little further back ; in an immature individual its origin hardly extends backward 
beyond the middle of m 1 . This abutment against the upper molar alveoli is strengthened, 
as the hind molars take more share in the work of mastication. The base of the process 
stretches forward and upward as far as the parallel with the first alveolus. 
A portion of the left upper maxillary of Nototherium, with d 4, in 1 , and m 2 , rather 
more worn than in the above-described specimen, exemplifies the same relation of the 
base of the malar process of the maxillary with the alveoli of the three anterior molars. 
