PEOFESSOE OWEN ON THE FOSSIL MAMMALS OF ATTSTBALIA. 
67 
and fourth in situ in a fragment of the right maxilla of a younger specimen. The entire 
molar series of both sides is shown in the cast of the skull in the Australian Museum 
(Plates II. & III.), and the left series in the cast of the left maxilla of another individual, 
probably female. Photographs of both these specimens, now in the Museum of Natural 
History, Sydney, New South Wales, have been transmitted to me, with the sanction of 
the Trustees of the Museum, by the kindness of the able Curator, Gekakd Kkefft, Esq., 
Corr. M.Z.S., &c. 
Of Nototherium inerme I have the entire molar series of both sides of the upper jaw ; 
and I infer, from a lithograph of “Australian Fossil Remains” sent me by Mr. Krefft, 
that the Museum at Sydney possesses a similar specimen. 
From these materials the characters of the upper molars of the present genus can be 
satisfactorily given. 
The series of live molars in the entire skull [Plate II. fig. 1, Plate III. fig. 3 (reduced), 
Plate IX. figs. 3 & 4, nat. size] occupies an alveolar extent of 7 inches 2 lines; it 
describes a slight convexity downward and also outward, the right and left series con- 
verging anteriorly (Plate III. fig. 3) in a rather greater degree than in JJiprotodon. The 
interval between the anterior lobes of the right and left last molars ( m 3 ) is 2 inches 
3 lines; that between the first small molars (d 3) is 2 inches. As in Diprotodon , the 
inner end of the front lobe of each two-ridged molar projects inward beyond the inner 
surface or contour of the antecedent tooth ; but the hind lobe does not project so far 
beyond the level of the front lobe of the succeeding tooth as in Diprotodon. 
The first upper molar ( d 3 ) may be said to be two-lobed, but is divided in an opposite 
direction to that in the rest of the series ; viz. into an outer and an inner, rather than a 
front and a back, lobe. The working-surface is subtriangular in form, the angles 
obtusely rounded, measuring in fore-and-aft extent 1 inch 1 line in the male Nototherium 
Mitchelli (Plate IX. figs. 3 & 4, d 3) ; the transverse diameter, posteriorly, is 11 lines. 
The outer lobe or division is the chief one, and constitutes the outer two thirds and the 
whole fore-and-aft extent of the tooth ; the outer side of its base swells out like part 
of a cingulum or ridge ; the summit is subcompressed, and seems to have been trituber- 
culate ; the inner and lower divisions consist of a larger hind tubercle and a smaller front 
one. On the whole, therefore, the tooth approaches the subsectorial type of its homologue 
in the Koala ( Pliascolarctos , Philosophical Transactions, 1871, p. 233, fig. 6 ,^ 4 ); it 
is implanted by two roots, one behind the other, the posterior being the largest and 
grooved anteriorly, as if preparatory to further transverse subdivision. 
The second molar (ib. ib. d 4 ) has a subquadrate working-surface, divided into two 
transverse wedge-shaped lobes («, b ), with an anterior (f) and a posterior (g) basal ridge ; 
the latter is the thickest, and developes a small tuberosity at its outer end. This ridge 
is continued upon the outer and inner borders of the hind surface of the hind lobe, and 
further upon the outer than the inner one. A short ridge closes the outer and inner 
ends of the transverse valley. The antero-posterior diameter of the crown is 1 inch 1 line, 
as is likewise the transverse diameter of the broadest part of the tooth. The direction 
k 2 
