PEOFESSOE OWEN ON THE FOSSIL MAMMALS OF ATJSTEALIA. 
215 
of the grinding-surface of m 2 ; in older examples it would show the same relation to m 3, 
as the grinders move, or seem to move, forward. 
I next proceed to notice the portions of skull of a more aged individual of Sthenurus 
Brehus from Clifton, Queensland. The laterally crushed maxillary part of the skull 
includes, with the incisors, the entire molar series of the left side and the major part of 
that of the right side. The premolar with a fore-and-aft length of 10 lines (20 millims.) 
in the type specimen ( loc . cit. plate xxvii. fig. 7, p 3 ) is but half a millimetre less in the 
present fluviatile fossil ; and this seems due to the wear of the anterior prominence. 
But all the formal characters are closely repeated. I have had no evidence from the 
spelaean haunt of the Thylacoleons of a giant Kangaroo which had attained the expe- 
rienced age of the original of the present Queensland fossil. The molar contiguous to 
p 3 contrasts, as usual, its great degree of wear with the fresher crown and higher level 
of the antecedent subsectorial tooth ; the fore-and-aft diameter, 6 lines (12 millims.), is 
the same in both fossils ; the minor transverse breadth in the Queensland specimen is 
due to the wearing down of the outer angles of the transverse lobes or ridges, which 
are prominent in the cave fossil. The superiority of size, slight as it is, in m 1 of the 
type subject of plate xxvii. figs. 5 & 6 (loc. cit.) is chiefly due to the minor wear of the 
crown of that tooth in the cave fossil. The last two molars occupy a longitudinal 
extent of 1 inch 6 lines (37 millims.) in both specimens. The linkless prebasal ridge 
is transverse, not curving at either end to be continuous with the corresponding angles 
of the fore lobe ; the low, short mid link is less distinctly continued to the inner angle 
of the fore lobe than in Sthenurus Atlas ; the depression on the hind surface, due 
chiefly to the ridge curving from the inner and hinder angle of the hind lobe toward 
the outer side of the base of the crown, with the lower and shorter ridge from the outer 
angle, are all characters of Sthenurus Brehus, repeated in the present as in the preceding 
Queensland sedimentary fossil. 
The left molar series in this instructive specimen occupies a longitudinal extent of 
3 inches 3 lines. 
The dentine is exposed on the fore lobe of the last molar, and the fore part of the 
enamel ridge of the hind lobe is nearly worn through ; the prebasal ridge also shows 
abrasion. A hollow transverse field of dentine is exposed on both lobes of the penulti- 
mate molar. With these indications of greater age the maxillary pier has retrograded 
and projects on the transverse parallel chiefly of the last, instead of the penultimate, 
molar as in the younger specimens (plate xxii. loc. cit.). In all the bony palate is 
entire. 
The fore part of the present skull shows a diastema 2 inches in extent. From the 
back of the socket of the third incisor to the fore part of the crown of the first is 1 inch 
3 lines. Of the third incisor, the seat of variety in existing Kangaroos, the left is lost, 
and of the right one only the fang remains. The crown of the second right incisor is 
worn nearly to its base. The first or front incisor is present in both premaxillaries, 
with its fang exposed in the left one. The crown is worn to the level of the palate ; 
