le continuity between
the existing fauna and flora of a country and those of the immediately
preceding age. A few of the more remarkable of these cases will now be
briefly noticed.

The mammalian fauna of Australia consists, as is well known, wholly of
the lowest forms--the Marsupials and Monotremata--except only a few
species of mice. This is accounted for by the complete isolation of the
country from the Asiatic continent during the whole period of the
development of the higher animals. At some earlier epoch the ancestral
marsupials, which abounded both in Europe and North America in the
middle of the Secondary period, entered the country, and have since
remained there, free from the competition of higher forms, and have
undergone a special development in accordance with the peculiar
conditions of a limited area. While in the large continents higher forms
of mammalia have been developed, which have almost or wholly
exterminated the less perfect marsupials, in Australia these latter have
become modified into such varied forms as the leaping kangaroos, the
burrowing wombats, the arboreal phalangers, the insectivorous
bandicoots, and the carnivorous Dasyuridae or native cats, culminating
in the Thylacinus or "tiger-wolf" of Tasmania--animals as unlike each
other as our sheep, rabbits, squirrels, and dogs, but all retaining the
characteristic features of the marsupial type.

Now in the caves and late Tertiary or Post-Tertiary deposits of
Australia the remains of many extinct mammalia have been found, but all
are marsupials. There are many kangaroos, some larger than any living
species, and others more allied to the tree-kangaroos of New Guinea; a
large wombat as large as a tapir; the Diprotodon, a thick-limbed
kangaroo the size of a rhinoceros or small elephant; and a quite
different animal, the Nototherium, nearly as large. The carnivorous
Thylacinus of Tasmania is also found fossil; and a huge phalanger,
Thylacoleo, the size of a lion, believed by Professor Owen and by
Professor Oscar Schmidt to have been equally carnivorous and
destructive.[189] Besides these, there are many other species more
resembling the living forms both in size and structure, of which they
may be, in some cases, the direct ancestors. Two species of extinct
Echidna, belonging to the very low Monotremata, have also been found in
New South Wales.

Next to Australia, South America possesses the most remarkable
assemblage of peculiar mammals, in i