52 
PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
of the arch as in other Marsupials. The muscular force operating on the mandible, both 
for biting and chewing, was very great, indicative of unusual resistance in the alimentary 
substances to be ground down. The grip of the front incisors brought by the shortness 
of the face and jaw within the power of the crotaphyte muscles in a degree proportional 
to the proximity of the inserted movers must have been like that of a vice. 
§ 3. The Mandible. A. Nototherium Mitchelli. — The mandible (Plate IV.) discovered 
in the bed of King’s Creek, a tributary of the river Condamine, Darling Downs, which 
was purchased of the collector by Mr. Benjamin Boyd, and subsequently, with the rest 
of Mr. Boyd’s collection, acquired by the British Museum, is from the same formation 
and locality as the skull above described, which fell into Mr. Isaac’s hands. 
This mandible agrees so closely, not only in the shape, structure, and other characters 
of the teeth, saving the difference of upper and lower, but also in the dimensions of these 
and of the proportion of the jaw-bone preserved, that it might well have been part of the 
same individual ; it certainly belongs to the same species. 
Comparing the type specimen of Nototherium Mitchelli , Ow.*, with the answerable 
part of the above-mentioned mandible, the correspondence in size and configuration 
is such as to support the reference of the present more complete specimen to that 
species. 
The depth of the mandible behind the last molar is 3 inches 9 lines in the first 
described, it is 3 inches 8 lines in the present specimen ; the thickness of the mandible 
below the last molar is 2 inches 6 lines in both specimens. The antero-posterior extent 
of the two last molars in the original fragment with mutilated crowns is 3 inches 4 lines ; 
in the more perfect mandible (Plate IV. figs. 1 & 2 ; Plate X. figs. 1 & 2, m 2, m 3) it is 
3 inches 6 lines; from the back of the last molar to the entry of the dental canal (Plate 
IV. fig. 2, 0 ) is 2 inches 9 lines in both specimens. The place and degree of inflection of 
the under margin and angle of the jaw (ib. a Sc d ) are the same in both. 
Referring on these grounds the mandible (Plate IV. figs. 1 & 2) to Nototherium 
Mitchelli , the cranium and upper jaw answering to that lower jaw must be referred to 
that species. 
The mandible in question consists of the two rami mutilated at both ends, but fortu- 
nately retaining their natural confluence at the symphysis, of which a longitudinal extent 
of 3 inches 8 lines is preserved (ib. figs. 2, 3, s ) ; this gives the angle of divergence of 
the horizontal rami from the place of confluence (ib. id.). It shows that the interval 
between the right and left mandibular condyles agreed with that between the articular 
cavities in the skull (Plate III. fig. 3, g, g ) ; and that the distance of the condyle from 
the fore part of the first molar (d 3 ) was the same as that, viz. 12 inches, from the fore 
part of the first molar to the joint for the condyle in the upper jaw. 
So much of the ascending ramus as is preserved, which closely corresponds with that 
in the type jaw, shows the same oblique direction of the curve (Plate IV. fig. 1, a, b, d) 
* “ Report on the Extinct Mammals of Australia, Ac.,” in Report of the British Association &c. for 1864, 
p. 13, pi. 4; and Cut, fig. 1, p. 42 (supra). 
