In its teeth, _Diprotodon_ shows itself to
be closely allied to the living, grass-eating Kangaroos; but
the hind-limbs were not so disproportionately long. In size,
also, _Diprotodon_ must have many times exceeded the dimensions
of the largest of its living successors, since the skull measures
no less than three feet in length. The other form in question
is _Thylacoleo_ (fig. 259), which is believed by Professor Owen
to belong to the same group as the existing "Native Devil"
(_Dasyurus_) of Van Diemen's Land, and therefore to have been
flesh-eating and rapacious in its habits, though this view is
not accepted by others. The principal feature in the skull of
_Thylacoleo_ is the presence, on each side of each jaw, of a
single huge tooth, which is greatly compressed, and has a cutting
edge. This tooth is regarded by Owen as corresponding to the
great cutting tooth of the jaw of the typical Carnivores, but
Professor Flower considers that _Thylacoleo_ is rather related to
the Kangaroo-rats. The size of the crown of the tooth in question
is not less than two inches and a quarter; and whether carnivorous
or not, it indicates an animal of a size exceeding that of the
largest of existing Lions.

[Illustration: Fig. 258.--Skull of _Diprotodon Australis_, greatly
reduced. Post-Pliocene, Australia.]

[Illustration: Fig. 259.--Skull of _Thylacoleo_. Post-Pliocene,
Australia. Greatly reduced. (After Flower.)]

The order of the _Edentates_, comprising the existing Sloths,
Ant-eaters, and Armadillos, and entirely restricted at the present
day to South America, Southern Asia, and Africa, is one alike
singular for the limited geographical range of its members, their
curious habits of life, and the well-marked peculiarities of
their anatomical structure. South America is the metropolis of
the existing forms; and it is an interesting fact that there
flourished within Post-Pliocene times in this continent, and to
some extent in North America also, a marvellous group of extinct
Edentates, representing the living Sloths and Armadillos, but
of gigantic size. The most celebrated of these is the huge
_Megatherium Cuvieri_ (fig. 260) of the South American Pampas.
The Megathere was a colossal Sloth-like animal which attained a
length of from twelve to eighteen feet, with bones more massive
than those of the Elephant. Thus the thigh-bone is nearly thrice
the thickness of the same bone in the largest of existing Elephants,
its circumference at