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Section IV.—The Austral Sub-region
The "island-continent" of Australia, as Mr. Wallace terms it, has, as has now been positively ascertained, a large portion of its interior so parched up and barren as to be almost destitute of animal life. But all along the east and south-east coasts, where there is land of sufficient elevation to condense the vapours from the adjoining ocean, more fertile districts are found. Besides the more widely diffused Australian types, some peculiar forms are met with only on this side of the continent. Tasmania, which is, in fact, but a recently separated piece of this portion of Australia, has also a moister and less extreme climate, and contains representatives of many of the special Australian forms, besides some indications of an autochthonous fauna.
The most peculiar mammals of Australia, and those which first claim our attention, are its representatives of the two forms which together constitute the Sub-class of Monotremes. These are the extraordinary genera Omithorhynchus and Echidna, which in their toothless jaws, in the conformation of their sternum and shoulder girdle, and especially in the structure of their reproductive organs, exhibit unmistakable signs of divergence towards the Classes of Reptiles and Amphibians. The first of these, usually known to the colonists as the " Duck-bill" or "Water-mole," (see Fig. 1, p. 23) is entirely aquatic in its habits, and is met with only in the streams and waterholes of New South Wales and Tasmania, where it burrows in the banks, and swims and dives with great facility. The Echidna, or "Spiny Ant-eater," is more widely distributed, and, as we shall presently see, has also representatives in the Papuan Sub-region. It inhabits the scrubs throughout the eastern districts of Australia, and is likewise occasionally found as far along the southern coast as Western Australia. In Tasmania a slightly different species (Echidna setosa) with
longer fur, almost concealing the spines (by some authors considered to be only a geographical race or sub-species of the typical form), is met with.
After the Monotremes, the most important group of mammals, and that which constitutes by far the most prevalent feature of Australian mammal-life, is the great order of Marsupials. Although not absolutely restricted to Australia, since one of its component families is purely American, the Marsupials, from their prevalence, constitute a still more noticeable feature of the Australian fauna than the Monotremes. Of the seven families into which this order is usually divided by naturalists, six are entirely confined to the Australian Region. Moreover, the Marsupials are so abundant in Australia proper, as to quite overshadow the few representatives of the higher orders of mammals found within its limits.
The carnivorous Dasyures (Dasyv/ridm) forming the first of these families take the place in Australia of the true carnivora of other parts of the world. They are seminocturnal in habits, and prowl about at dusk in search of the smaller mammals and birds which constitute their food. In Tasmania two peculiar forms of Dasyures occur, which are not met with in the Australian continent. These are the Thylacine, a dog-like animal with a long tapering tail, noticeable as being the largest of living carnivorous Marsupials (Fig. 2, p. 25), and in general external appearance so much resembling our familiar domestic friend that the uninitiated can hardly be persuaded that its proper place is in a different order of mammals; and the Sarcophilus tirsinus, or Tasmanian Devil, as it is popularly called—a somewhat aberrant dasyure of a prevailing black colour, about the size and somewhat of the shape of an English badger, and remarkable for its savage and voracious disposition. Both these animals, now confined to the island of Tasmania, must have formerly extended into Australia, as their remains have been found fossil in the caves of the Wellington Valley of New South Wales. Altogether the Dasyures number some twenty species in Australia and Tasmania.
Besides the Dasyures, a second type of the same family, but in many respects divergent in structure, is found on the mainland of Australia. This is the Myrmecdbius, or Banded Ant-eater, a little animal of the size and somewhat
of the likeness of the common squirrel, with a long bushy tail and elegant transverse stripes across the back. The Myrmecobius is terrestrial in its habits, and feeds principally on ants. It is apparently confined to the western and central parts of the sub-region.
The Peramelidm, or Bandicoots, the second family of Australian marsupials, have also teeth adapted to an insectivorous diet, although we know, from the records of trustworthy observers, that some of the species feed more or less upon vegetable substances. Such is certainly the case with the Rabbit-eared Bandicoot (Perogale lagotis) of Western Australia, which is abundant over the grassy plains of that colony, and, from its burrowing habits and large hare-like ears, is commonly known as the "Native Rabbit." Of the typical bandicoots (Peromeles), five or six species are known, distributed over various portions of Australia, each colony having its peculiar forms. They are all purely terrestrial animals, some inhabiting the densest scrubs, and others the hot stony ridges of the upland plains. The only remaining member of the family PeromelicUe is the anomalous Pigfoot (Choeropus castanotis), a small ratlike animal with slender feet, which is confined to the hard stony grounds of the interior of the southern Australian colonies.
A most interesting discovery has recently been made in the deserts of Central Australia of a new burrowing marsupial, of mole-like habits, for which it is necessary to constitute a new family. This little animal has been described by Dr. E. C. Stirling (9) under the name of Notoryctes typhlops, and is apparently very rare (Fig. 3, p. 27). As its name implies, it is quite blind, its eyes being represented merely by pigment spots buried beneath the skin and muscles; furthermore, its whole structure is admirably adapted for its burrowing life. Full descriptions of both its habits and anatomy will be found in the Transactions of the Royal Society of South Australia for 1891.
We now come to the herbivorous marsupials (Diprotodontes), of which there are three families all confined to the