10 
MARSUPIATA. 
nivorous and insectivorous species, in which there are more 
than six incisors in the upper jaw, distinct canines, and at 
least two false molars on either side of each jaw: a second 
type is presented by the Kangaroo group, where the canines are 
wanting, or very small, and there exists hut one false molar 
on each side of the jaw; from these latter herbivorous species 
should he separated the Wombat, in which the molar and 
incisor teeth differ in being rootless, and the latter are reduced 
in number as before stated. But we have yet to notice another 
large group, the PJialangistida 1 , in which we find the tectli 
presenting intermediate conditions to the two great sections 
just mentioned; they differ from the first section in having 
hut six incisors in the upper jaw, and in having the two fore¬ 
most incisors of the lower jaw very large and nearly horizontal, 
and the other's rudimentary or wanting; there is also con¬ 
siderable difference in the form of these teeth. From the 
second section they differ in the structure of the molar teeth, 
as will hereafter he pointed out, and (with one exception only 
—the Koala) in having more than one false molar to each side 
of each jaw. 
In the various species composing the sections noticed in the 
following Table, wherever the inner toe of the hind foot is 
developed, it assumes the form of a thumb, and is opposeable 
to the other toes, and thus gives a prehensile power to the 
hind foot, adapting it to climbing: lienee we find the thumb 
developed in all climbing species, whether carnivorous, insec¬ 
tivorous, or herbivorous; but in the ground-inhabiting species 
of each of these sections, the inner toe of the hind foot is 
reduced to a rudimentary condition, or wanting; in both the 
herbivorous and animal-feeding groups, however, wo find a 
gradual transition from the thumbless to species possessing a 
well-developed thumb. In the Didelphidio , for instance, the 
thumb is in many well developed ; in others it becomes very 
small, as in some of the Dasyuridiv; and in this last men- 
