PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
73 
angle of the inner border of the lobe than in d 4, and it passes outward to the base of 
the outer end of that lobe, like a “ cingulum,” without being continued upward into 
the outer prominence bounding that part of the front surface of the front lobe (tig. 3, m 1). 
This surface, as in the second molar, is finely rugous ; it is concave transversely, convex 
vertically. The cingulum rises to a point, forming an angle upon the outer side of the 
base of the anterior lobe (fig. 1, m 1). The closing ridge of the valley is formed by its 
continuation backward from the angle, and is limited to the outer entry. The hind basal 
ridge ( g ) is thicker than in d 4. 
The two lobes are not on the same parallel, but rather “ en echelon ,” the hind one 
rising more mesially or internally, and its inner and fore angle looking forward clear of 
that of the other lobe. The unworn summits are more bent backward than in d 4. 
The fore-and-aft extent of m 1 is 1 inch 6 lines ; the transverse diameter of the base of 
each lobe is 1 inch. 
In the partially exposed calcified germ of m 2 (ib. figs. 3 & 4) the summits of the two 
lobes are not quite parallel, and the hind border of the hind lobe slopes more backward 
to a well-developed basal ridge. 
The smooth shallow cavity behind the alveolus of m 2 is plainly the beginning of the 
formative chamber of m 3, calcification of which had probably not begun. 
I regret not to possess specimens of Nototherium showing stages of mandibular 
dentition between that above described and the subject of Plate X. fig. 3. 
This specimen forms part of a collection of fossils from the deposits of Darling Downs 
made by Henry Hughes, Esq., and now in the Museum of the Natural-History Society 
of Worcester, to the Council of which I am indebted for the opportunity of examining, 
comparing at the British Museum, and figuring instructive evidences of extinct Austra- 
lian Mammals. The one which is referable to Nototherium is the right ramus of the 
mandible with the last three molars in situ, the fangs of the second and part of the 
alveolus of the first molar. The two fangs of the second molar (ib. d 4) show a fore-and- 
aft extent of at least 1 inch 2 lines for the crown of that tooth, w r ith an extreme breadth 
of eight lines. That a still smaller tooth preceded it is indicated, as before remarked, 
by a part of its socket ( d 3). The shape of that tooth, generically distinguishing Noto- 
therium from Diprotodon, is instructively shown in the preceding specimen (Plate VI.). 
The antepenultimate tooth, or third counting backward (Plate X. fig. 3, m 1), measures 
1 inch 6 lines in long diameter, and 1 inch 2 lines across the hinder lobe; the talon (g) 
at the back of this lobe is as well developed relatively as in the penultimate molar. The 
ridge (r) or production of the outer and front angle of the back lobe obliquely toward 
the middle of the front lobe is conspicuous at this stage of attrition ; much of the front 
lobe has been broken away. 
The crown of the penultimate molar ( m 2) is in length 1 inch 8 lines, in breadth 
1 inch 3 lines, in height 8 lines; the dentine is exposed at the summit of each ridge. 
The two ridges, or bilophodont type, of the molars of Nototherium were indicated rather 
than demonstrated in the specimens on which the genus was founded. The restoration 
MDCCCLXXII. l 
