568 
PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTKALIA. 
three existing families with special modifications, respectively, for burrowing, climbing, 
and leaping; or, to borrow a figure from another hypothetical school, I might remark 
that the orders, or other natural groups, of placental Mammalia represented by members 
of the marsupial series have been indicated by different zoologists*, and with no material 
divergence of opinion ; but not until now has evidence been received of a Marsupial 
representative of the proboscidian group. 
In certain Mastodons there is a pair of incisive tusks below as well as above : the 
proboscidians maximize the rodent type as Diprotodon does the Marsupial one. The 
brain of the Elephant is essentially “ lissencephalous,” inasmuch as the cerebrum does 
not extend upon the cerebellum. This position of one primary mass of brain in front 
of the other is, as stated in the definitions of the subclasses of Mammalia in the cere- 
bral system f, a more constant and important character than convolution of surface,- 
which in both ly- and liss-encephala relates to the bulk of the species and of the brain. 
So, on the other hand, if a smooth cerebrum overlaps the cerebellum as in the Marmoset, 
it is essentially “ gyrencephalous.” The terms suggested by the superficial character 
which prevails, with exceptions, are arbitrary, but the most convenient for expressing 
the more constant characteristics of the brain therewith associated. 
In the extinction of Diprotodon, as of Megatherium , there seems to be an additional 
exemplification of the fruitful and instructive principle which, under the phrases “ contest 
for existence,” or “ battle of life,” embodies the several circumstances, such as seasonal 
extremes, generative power, introduction of enemies, &c., under the influence of which 
a large and conspicuous quadruped is starved out, or falls a prey, while the smaller ones 
migrate, multiply, conceal themselves, and escape. 
We infer from the fact of remains of young and inexperienced Diprotodons occurring 
in Australian Caverns with those of Thylacoleo, that the large Marsupial herbivore had 
its enemy in, and occasionally fell a victim to, the large Marsupial Carnivore J; as at the 
present day the Kangaroo is laid in wait for by the Thylacyne, or ‘Native Wolf’, and 
the Dasyure, or ‘ Native Cat.’ 
We may speculate upon the possible relation of the first introduction of the Human 
kind into Australia, and of the subsequent insulation of that land from the rest of the 
Papuan Continent, to the final extinction in the so restricted territory of all the charac- 
* “ On dirait, en un mot, que les marsupiaux torment une classe distincte, parallele a celle des quadrupedes 
ordinaires et divisible en ordres semblables ; en sorte que si on plaoait ces deux classes sur deux colonnes, les 
sarigues, dasynres et perameles seraient, vis-a-vis des carnassiers insectivores a longues canines, tels que les 
tenrecs et les taupes ; les pkalangers et les potoroos, vis-a-vis des kerissons et des musaraignes ; les kangaroos 
proprement dits, ne se laisseraient guere comparer a rien ; mais les pkascolomes devraient aller vis-a-vis des 
rongeurs.” — Cuvier, Regne Animal, ed. 1817, tom. i. p. 171. “ Les ornitkorkynckes et les eckidnes y formeraient 
un groupe parallele a celui des edentes.” — Op. cit. ed. 1829, tom. i. p. 174. 
f Owen, “ On tke Ckaracters &c. of tke class Mammalia,” Proceedings of tke Linnean Society, 1857. 
t I skall return to tke question of tke evidence of tke carnivority of Thylacoleo in a suksequent commu- 
nication. 
