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1. The Order of Marsupials consists of about 172 species divided into thirty-nine genera and eight families.
2. Six of these families (with thirty-six genera and 144 species) belong to the Australian Region; the remaining two families (with three genera and twenty-eight species) are Neotropical.
3. Two species of Phalanger have passed the northern boundaries of the Australian Region into Celebes which is in the Oriental Region (see Chapter V., p. 146).
4. In a similar way a single form of Opossum (Didelphys) is found in the southern part of the Nearctic Region.
5. With these exceptions no Marsupials are found in the Palæarctic, Nearctic, Oriental, and Ethiopian Regions.
SECTION VI.—DISTRIBUTION OF MONOTREMES The geograpical limits of the fourteenth and last order of mammals may be very easily pointed out, the Monotremes (which are correctly regarded as a sub-class, Prototheria) being absolutely restricted to the Australian Region and found even here only in certain parts of it. The Monotremes in these days are a failing group, consisting only of about five species, which belong to three genera and two families—the Echidnidæ or Echidnas, and the Ornithorhynchide or Duck-bills. Echidna, the first-known genus of the former family, is somewhat widely distributed from New Guinea over the whole of Australia and Tasmania The Papuan, Australian, and Tasmanian forms of Echidna, which are closely related,
are classed by some naturalists as species, and by others as sub-species. It is preferable to place them in the former category, as no intermediate forms are certainly known. But in Papua, besides typical Echidna, the family is also represented by its larger brother, Proechidna, with a single well-known species (Proechidna bruijni) and perhaps another species not yet certainly distinguished.
The second family of Monotremes embraces only the excessively anomalous aquatic and fossorial form commonly known as the Duck-bill (Ornithorhynchus anatinus). The Duck-bill occurs in Northern Queensland, and spreads southwards thence into New South Wales, Victoria, and South Australia. It is likewise found in Tasmania, but so far as we know has never yet been obtained in any part of Western Australia.
Table of the Order Monotremata, showing the distribution of the species.
DEDUCTIONS 1. The Order of Monotremes contains five species referable to three genera and two families.
2. It is entirely restricted to the Australian Region.
SECTION VII.- FINAL CONCLUSIONS
Thus we see that whether we take the Mammals in Geographical or in Systematic order, we arrive at nearly the same result—namely, that the best Primary Geographical Divisions of the earth are six in number. Of these the Australian Region (Neogxa), in which the Mammalfauna is pre-eminently Marsupial, and embraces the whole Order of Monotremes, is by far the most distinct. It is, however, also easy to separate the Neotropical Region (Notogæa), with its one family of Marsupials and numerous Edentates. The remaining Regions (Arctogæa), may be grouped together, but are still separable-on more slender grounds, it is true, into four divisions — the Ethiopian Region remarkable for its abundant Ungulates, the Giraffe, and the Hippopotamuses, the Oriental known by its Orangs, Gibbons, and Tapir, and the Palæarctic and Nearctic, which, no doubt, present many points of similarity as regards their Mammal-faunas, but may nevertheless be properly kept apart. The Nearctic Region, as has been shown above, has been overrun by an inroad from the northern portion of the Old World, but has a strongly developed under-stratum of endemic forms mixed up with some Neotropical types, which are utterly foreign to the Palearctic Region.