EXTINCT FAMILIES 171 
EXxtTINcr FAMILIES. 
Here may be noticed two genera of extinct Marsupials, the remains 
of which have been found in the Pleistocene deposits of Australia, 
which agree with the Macropodide and the Phalangeride in having 
2. incisors, those of the lower jaw being very large and proclivous. 
As the whole of their structure, especially that of the hind feet, is 
not yet known, their precise affinities cannot be determined. 
Diprotodon.t—Dentition : 1 3, ¢ 2, p 4,m 4; total 28. The first 
upper incisor very large and scalpriform (Fig. 56). True molars 
with prominent transverse ridges, as in Macropus, but wanting 
the longitudinal connecting bridge. Anterior and posterior limbs 
less disproportionate than in the Kangaroos. Humerus elongated, 
and differing from that of nearly all Marsupials in the absence of an 
Fic. 56.—Left lateral aspect of the skull of Diprotodon australis ; from the Pleistocene of 
Australia, jp; natural size. i, Incisors; p, premolar; m, molars. (After Owen.) 
entepicondylar foramen. ‘The palate is fully ossified, and there is 
no pit or perforation in the masseteric fossa of the mandible. D. 
australis is the largest known Marsupial, being fully equal in bulk 
to a Rhinoceros. It may be regarded as the type of a family— 
Diprotodontide—having affinity on the one hand with the Phalangers 
and on the other with the Kangaroos. 
Nototherium.2—Represented by a species of somewhat smaller 
size than the type of Diprotodon, with a shorter skull, in which the 
zygomatic arches are very wide and the nasals curiously expanded 
at their extremities. The mandibular symphysis is ankylosed ; 
1 Owen, in Mitchell’s Eastern Australia, 2d ed. vol. ii. p. 362 (1838). 
2 Owen, Cat. Mamm. and Aves, Mus. R. Coll. Surgeons, p. 314 (1845). 
