214 
PEOEESSOR OWEN ON THE EOSSIL MAMMALS OE AUSTRALIA. 
the prominent part of the opposed first incisor ; the crown of the third incisor (« 3) 
presses closely against that of the second : thus firmly interlocked the three incisors in 
each premaxillary worked as one tooth. The enamel of the second and third incisors is 
continued from the outer or fore part of the crown upon part of the hind or inner 
surface ; but the enamel of the large anterior incisor is limited to the fore part. In 
both proportion and curvature the large incisor resembles the homologous tooth in 
Nototherium and Biprotodon ; but it is an incisor of limited growth, and its implanted 
fang tapers to the end, as in the rest of the family Macropodidoe . 
From the back of the median border of the front incisor (Plate 28. fig. 3, i 1) to the 
fore border of the “foramen incisivum” (ib. a) is 1 inch 6 lines; from this border a 
groove is continued forward, shallowing, to near the tooth. 
The breadth across the outsides of the last pair of incisors is 1 inch 11 lines ; the 
breadth of the palatal part of the premaxillaries at the fore part of the prepalatal or 
incisive foramina is 1 inch 10 lines. From the third incisor to the premolar is 
2 inches 1 line ; in other words, this is the extent of the diastema or toothless space 
(Plate 28. fig. 1, d, i 3) between the incisors and the molars. The breadth of the bony 
palate anterior to the premolars is 2 inches 1 line. 
To the objection that the species Atlas and Brehus of the genus Sthenurus might 
have been based, in Part VIII., on parts derived from the female and male of the same 
species, the reply is that, although the males exceed in size the females in most, if not 
all, Kangaroos, the difference is chiefly shown in the bones of the trunk and limbs, less 
so in the skull, and little, if at all, in the teeth. 
Now the third incisor is, relatively to the first incisor, smaller in Sthenurus Brehus 
than in Sthen. Atlas. In the larger species the length of the molar series (Plate 28. fig. 1, 
p 3 -m 3) is 3 inches 6 lines, in Sthenurus Atlas it is 2 inches 9 lines. The premolar 
(p 3) exceeds the rest in fore-and-aft diameter, which, as in the cave specimen ( loc . cit. 
plate xxvii. fig. 7, p 3), is 9|- lines (20 millims.) ; the three low transverse ridges which 
connect the inner with the outer wall are well marked in the present comparatively 
young though full-grown individual. These ridges become less salient in the course 
of the oblique wear of the crown of the premolar from the outer to the inner ridge, 
and in old individuals they are polished off. But all the generic and specific characters 
of the premolar of Sthenurus Brehus from Mitchell’s Breccia-cave in New South Wales 
are repeated in the present specimens from the fluviatile beds of Queensland. The 
same may be said of all the succeeding molars which in the type specimen are suffi- 
ciently complete for comparison. The last molar in the present example (Plate 28. 
fig. 3, m 3) has not quite come to the grinding level, and its ridges are untouched. 
The enamel-fold from the inner angle to the hind ridge, which defines by its oblique 
tract along the hind surface the angular depression there, seems as if it were folded on 
itself or notched at its basal termination. 
The descending process of the zygoma is more perfectly preserved than in any other 
fossil hitherto transmitted to me of the genus Sthenurus ; it terminates below the level 
