132 MARSUPIALIA 
In certain species, as the Opossums, Dasyures, and Thylacine, 
the incisors are numerous, small, and subequal in size, and the 
canines large, as in the typical placental Carnivores (Fig. 35). 
To these the term “polyprotodont” is applied, and they are all 
more or less carnivorous in their habits. In others the central 
incisors are very prominent, and the lateral incisors and canines 
absent or subordinate in function (Fig. 36). These are called 
“ diprotodont,” and they are all wholly or in great part vegetable 
feeders. In one group of these, the Wombats, there are but two 
incisors above and the same number below; but all the others, in- 
cluding the Kangaroos, Koalas, and Phalangers, have two functional 
incisors below and as many as six above, three on each side, but 
of these the first or central pair is the most fully developed. 
Some hesitation has frequently been expressed as to whether the 
Polyprotodont and Diprotodont types are entitled to constitute 
distinct primary groups, owing to the presence of syndactylism 
among the Peramelide in the former, as well as in the latter ; but if 
Mr. O. Thomas is right in regarding this feature as acquired 
independently in the two groups we may safely adopt such a 
division. Taking various combinations into consideration, the 
existing Marsupials readily group themselves into six very natural 
families, the leading characters of which may be summarised as 
follows :— 
Order MARSUPIALIA. 
A, Potyproropontia.—Incisors numerous, small, subequal. Canines 
larger than the incisors. Molars with sharp cusps. 
a. Incisors 3. Hind feet with the four outer toes subequal, 
distinct, and a well-developed opposable hallux. Didel- 
phyide. 
. Incisors $. Hind feet with four outer toes distinct. Hallux 
small or rudimentary, rarely opposable. Dasyuride. 
(4—5) 
= 
y. Incisors Hind feet long and narrow. Fourth toe 
larger than the others. Hallux rudimentary or absent. 
Second and third toes very slender, and united in a 
common integument (syndactylous). Peramelide. 
B. Diproropontia.—Incisors not exceeding $, usually 3, but occasion- 
ally +. Central (first) upper and lower incisors large and 
cutting. Upper canines generally, and lower invariably, absent 
or small. Molars with bluntly tuberculated or transversely 
ridged crowns. 
a. Teeth with persistent pulps. Incisors 4, large, scalpriform, 
with enamel on the outer surface only. No canines. 
Hind feet with four subequal outer toes, partially 
syndactylous, and with rudimentary hallux. Phascolo- 
myidee. 
