76 
PEOFESSOE OWEN ON THE FOSSIL MAMMALS OF AUSTEALIA. 
me by the cast, Plate V.), the molars show almost the same stage of attrition as in the 
preceding specimen. The first and second molars are retained on the left side. The 
crown of the first (cl 3) is worn down to a flattened uniform surface, showing the same 
posterior breadth as in the entire crown in the immature jaw. The two roots supporting 
it have now risen nearly half an inch above the socket. The dimensions and proportions 
of the following four grinders closely accord with those in the mandible, the teeth of which 
are figured of the natural size in Plate IX. fig. 3. 
In the part of the right ramus of Nototherium Mitchelli with the three last molars 
and the back part of the symphysis, the molars are worn nearly to the same degree : 
their antero-posterior extent is 5 inches 2 lines. The left ramus of the same species, 
more mutilated anteriorly, but with a greater proportion of the ascending branch, 
shows the last two molars similarly worn. The enamel in these Nototherian specimens 
is as thick as in Diprotodon. 
In a mandibular fragment with the lobes of the last molar worn down to the valley, 
the anterior root of the penultimate molar is exposed, showing a strong curve convex 
forward, with a deep anterior longitudinal indent almost dividing the implanted end 
(Plate X. fig. 8). The fine rugosity of the cement, repeated on the closely clasping 
wall of the socket, is here well shown. 
The molars (Plate X. figs. 4, 5, 6) in the mandible of Nototherium Victoria? (Plate VII.) 
show nearly the same stage of attrition as in the Worcester specimen of N. Mitchelli 
(Plate X. fig. 3). 
As already stated, they are limited to the last three teeth and a fragment of the one 
in advance. In m 1 the ridge closing the outer entry of the valley (h, figs. 4 & 5) 
developes an enamel tubercle; and there is a smaller one at the inner entry (hi, fig. 6). 
Of this there is no trace in the perfect specimen of that molar in the immature jaw of 
Nototherium Mitchelli (Plate VI.), and only a very feeble indication of such on the outer 
side. The rudiment of the “ link ” or ridge (r) from the hind lobe to the middle of 
the base of the hind surface of the front lobe is well marked in N. Victories. The hind 
talon (g) closely overlaps so as to interlock with the front talon (f) of the penultimate 
molar, m 2 . The abraded surfaces of the two lobes slope from before downward and 
backward. The fore-and-aft diameter of m 1 is 1 inch 6 lines. 
The fore part of the penultimate molar (fig. 4, a , m 2 ) rises half an inch above the 
overlapping talon (g) of the antecedent tooth, at the outer and inner ends of which the 
front talon of m 2 appears. Externally it curves up to terminate near the base of the fore 
and outer part of the front lobe ; on the inner side it sooner subsides. The greater 
breadth, as compared with m 1 of the front lobe, is gained chiefly by extension of the 
inner part. A ridge, beginning at the back part of the outer end of the front lobe, 
curves down to the outer entry of the valley, developes there a tubercle, and curves up 
the outer side of the hind lobe, whence a similar ridge curves downward and backward 
to the hind talon ; the middle and thickest part of this is undermined by the smooth 
surface which overlies the front talon of the last molar (f, m 3). 
