PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
75 
may gain increase of support, by enlargement of the fangs before they become solidified, 
as in the broken one in the present specimen. The difference of size may likewise be 
referred to difference of sex ; it would be hazardous to predicate a difference of species 
on this ground. In both examples they come near, in size, to the anterior molar ( d 3 ) in 
the upper jaw of Not other ium Mitchelli. 
The socket of the second molar (Plate X. figs. 1 & 2, d 4 ) has a fore-and-aft extent 
of 1 inch 1 line, which accords closely with that in Plate VI. figs. 1-5, d 4). 
The third molar (Plate X. figs. 1 & 2, m 1 ) shows both lobes abraded to their base ; 
the enamel still crosses the valley, but that between the hind basal ridge and the hind 
lobe is worn away and a broad smooth expanse of dentine and osteodentine is exposed, 
11 lines by 6 lines in diameter. The fore-and-aft extent of the remaining basis of the 
crown is 1 inch 6 lines; the breadth of the hind lobe is 1 inch. These dimensions 
accord sufficiently closely for specific identity with those of m 1 , in the immature subject 
of Plate VI. 
In m 2 (Plate X. figs. 1 & 2) the enamel of the hind lobe is worn down to the level 
of the hind basal ridge, which is partly abraded, but not down to the dentine. The 
narrower and lower anterior basal ridge is intact, and the enamelled crest of the anterior 
lobe rises 3 lines above it. The anterior productions (r, r) of the two lobes, rudi- 
mentally indicating the linking bars in certain Kangaroos, are instructively marked at 
the present stage of attrition. The posterior basal ridge of this tooth overlaps the ante- 
rior one of the next (m 3), the front lobe of which rises 5 lines above that level. The 
anterior prominence near the outer end of each lobe repeats the short forward angle in 
the contour of the enamel as here worn down. The corresponding prominence of the 
hinder lobe (r) inclines toward the middle of the valley ; the macropodal affinity, slight 
as it is, is more strongly marked in Nototherium than in Diprotodon *. 
The fore-and-aft extent of m 3 is 1 inch 10 lines, exceeding by 2 lines that of the 
opposing molar above (Plate IX. fig. 4, m 3) : in this, also, a macropodal character is 
repeated. The transverse extent of the front lobe of m 3, fig. 3, is 1 inch 4 lines ; that 
of the hind lobe is less. 
The entire extent of the lower molar series is 7 inches 2 lines, about 2 lines less than 
that of the upper molar series in the skull of Nototherium Mitchelli (Plate II. fig. 1). 
In the series of sockets of the lower jaw of possibly the same individual, the partition 
between the fore and hind fangs of each tooth is much thicker than that between the 
sockets of distinct teeth. The transverse space between the hind lobes of the right and 
left last lower molars is 2 inches 9 lines ; between the front lobes of the first molars 
1 inch 5 lines. Each mandibular series describes a very slight curve as it advances 
forward, with the convexity outward. The base of the socket of the incisor, which does 
not extend beyond that of the first molar, is 1 inch 2 lines in vertical diameter, 8 lines 
in transverse diameter. 
In the specimen of the mandible with the symphysis entire, or nearly so (known to 
* Compare figures 11 & 18, Plate xl. Philosophical Transactions, 1870, with figures 1, 2, & 3 in Plate IX. 
L 2 
