PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
77 
The fore-and-aft extent of m 2 is 1 inch 9 lines ; the transverse breadth of the front 
lobe is 1 inch 2-$ lines, that of the hind lobe is 1 inch 1 line. The abraded surfaces 
of the summits of these lobes slope, as in m 1 , in the same direction but in a greater 
degree. The hind root of m 2 is exposed by the fracture shown in figs. 1 & 2, Plate 
VII. ; it inclines somewhat backward as it sinks in the socket ; its basal breadth at the 
outlet of the socket is 1 inch ; it contracts, in the same direction, to 7 lines ; much of 
its surface shows minute granulate longitudinal striations. 
The last molar (Plate X. figs. 4, 5, 6, m 3) rises above and projects inwardly beyond 
the preceding, in the same degree as m 2 does in relation to m 1 . The festoon character 
of the ridges curving toward the outer entry of the valley and to the hind talon is repeated 
in greater strength ; the outer closing tubercle (fig. 4, h) is less marked than in m 1 , but 
is conspicuous, as is that in the ridge closing the inner entry (fig. 5, h'). I incline to 
regard these tubercles as constant, and as differentiating the last two molars of the present 
species from those of Nototherium Mitchelli. A mere linear tract of dentine is exposed 
on the obliquely worn apices of the transverse ridges of rn 3. The fore-and-aft diameter 
of this molar is 1 inch 10 lines; the transverse extent of the abraded summit of the 
hind lobe is 10 lines, but that of its base is 13 \ lines, the same diameter of the front 
lobe being 15 lines. The enamel in Nototherium Victorias is not so thick as in N. Mit- 
chelli ; its surface is similar. 
When the skull, or upper jaw, of this species may be found in South Australia, it will 
yield, as in the case of the Queensland specimen, the characters ascribed by Macleay to 
Zygomaturus , with, probably, better marked specific characters than those of the lower 
jaw. 
No mandible or mandibular teeth, referable or adaptable to those of the maxilla in 
the unique subject of Plates II. & III., have yet been discovered, save those which yield 
the characters of the genus Nototherium . No skull adaptable to the mandible and man- 
dibular teeth of Nototherium has yet been discovered, save that to which the name 
Zygomaturus was given. The admission, therefore, into palaeontological catalogues of 
two genera of bilophodont Marsupialia of the bulk of Nototherium awaits the discovery 
of fossils demonstrating the distinctive characters of such. 
Taking a retrospect of the dental characters of the genus Nototherium with reference 
to a comparison with those of the genus Liprotodon, we find that the indications, few 
and feeble though they seemed in the mutilated mandibles and mandibular dentition 
first received *, have been supported and the inferences therefrom verified in a striking 
and unexpected degree by the characters of the rest of the skull and of the maxillary 
dentition. 
The first molar, for example, does not give, in miniature, the bilophodont character 
of the other and larger molars ; its crown answers rather to the outer half of the two- 
ridged grinder with a rudiment of the inner half of the hinder transverse ridge or lobe. 
