pialia_, and comprises all
opossums (_Didelphys_), kangaroos (_Macropus_), phalangers
(_Phalangista_), the Tasmanian wolf (_Thylacinus_), the dasyures
(_Dasyurus_), the bandicoots (_Perameles_), and their allies. With the
exception of the true opossums (_Didelphys_), all the members of the
order are found in Australia or its vicinity, and nowhere else in the
present day; although, as we shall better see hereafter, Europe once
possessed animals closely allied to Australian forms of to-day--notably
to a pretty little quadruped which bears the generic name _Myrmecobius_.

As last of the class of beasts, we have two extremely exceptional
mammals (both found only in the Australian region), the duck-billed
platypus (_Ornithorhynchus_), and the _Echidna_. The first of these, as
its name implies, has a muzzle quite like the bill of a duck, with a
squat, hairy body, and short limbs. The echidna is covered with strong,
dense spines, and has a long and slender snout. These creatures together
form the order _Monotremata_--an order which differs very much more from
any other Mammalian order than any of the other orders of mammals differ
one from another.

Thus, that great group which embraces man and beasts, and which group
ranks as a "class"--the _class_ Mammalia--comprises (as we have now
seen) a number of subordinate groups termed "orders," the orders being
made up of families, and these again of genera.

It would be impossible as yet (when hardly any anatomical facts have
been even referred to) to give the characters of the class _Mammalia_.
It must at present suffice to point out that, in addition to mammary
glands, the creatures have hot blood, and the body bears more or less
hair--at least at some time of life.

We may now pass to the next class, that of birds--the class _Aves_. In
spite of the great multitude of kinds which ornithologists
enumerate--upwards of ten thousand species--there is very much less
diversity of form amongst birds than there is amongst beasts.

Starting in the present class as in the preceding one from the most
familiar kinds, we may begin with the domestic fowl. This is one of an
"order" to which belong the peacock, all pheasants and tragopans (three
forms which have their home in Central and Southern Asia), also the
Guinea fowls (African forms), and the turkeys and curassows, which are
American representatives of the order. Besides these may be mentioned
partridges, grouse, black-cock, the caper