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only two species have as yet been discovered, one from the mountains of Ecuador and the other from the interior of Colombia.
The fourth and only remaining family of Diprotodont Marsupials is the Phascolomyidæ, or Wombats, of which three species are generally distinguished, all belonging to the more temperate regions of Australia and extending into Tasmania, to which island Phascolomys ursinus is restricted.
SECTION IV.—DISTRIBUTION OF POLYPROTODONT
Like the Diprotodonts the Polyprotodont Marsupials now known embrace three Australian and one American family, which are all, as already remarked, generally carnivorous and insectivorous and but rarely omnivorous in their diet. The Peromelidæ, or Bandicoots, which are placed at the head of the list, are very distinct in structure and sharply defined from their relatives by the syndactylism of the hind feet, consist of three genera onlyPerogale, which is restricted to the continent of Australia, and Peromeles, which ranges over New Guinea, the Moluccas, and the New Britain group, its representatives in these islands being specifically distinct. The last genus is a very peculiar little animal, the Pig-footed Bandicoot (Choropus) which is restricted to the Australian continent.
Between the Peromelidæ and the Dasyurida is perhaps the best place for the very anomalous mole-like form of Marsupials which has recently come to light in Central Australia. We need not again descant on the extraordinary form and habits of Notoryctes typhlops, the sole representative of the family Notoryctidæ, an inhabitant of the most barren and desolate regions of the Australian Continent.
In the Dasyuridæ, under which family are ranged the most purely carnivorous animals of the Australian mammal-fauna, we have a widely diffused and more numerous group consisting of some seven genera and about twenty-eight species. The largest of these is the Thylacine, now confined to Tasmania, but formerly found also on the adjoining continent. Its extraordinary dog-like appearance strikes the ordinary spectator with astonishment, when he is told that it is in no way nearly related to the Canidae. It is, however, truly and purely carnivorous in its habits, as is its smaller ally Sarcophilus ursinus, also in these days entirely restricted to Tasmania. The Dasyures (Dasyurus), of which five species constitute the next genus, are the largest carnivorous mammals now existing in Australia, where four species are recognized, a fifth being restricted to New Guinea. The three next genera of Dasyuride contain numerous small insectivorous forms, which are found in the Papuan Subregion as well as in Australia. The series of Dasyures is concluded by the peculiar little form Myrmecobius, or “ Marsupial Ant-eater” as it is often called. This is so different from the typical Dasyures that it may be more correctly regarded as constituting a family by itself, and is of special interest as being generally supposed to be a near relative of the Mesozoic Polyprotodont Marsupials of the Jurassic beds of England.
We now come to the eighth and last family of the Marsupial Order. It consists of the Opossums, which are, as already stated, peculiar to the Neotropical Region, where they seem to take the place of the absent Insectivores. The Opossums are best arranged in two genera only, Didelphys with about twenty-five species, and the very distinct Water Opossum (Chironectes) with a single species only. The Tree Opossums (Didelphys) of which Mr. Thomas recognizes five sub-genera, are distributed all over the Neotropical Region and a single species, Didelphys virginiana, is a well-known inhabitant of the southern United States, and is therefore unquestionably a Nearctic mammal. Whether, however, it is certainly indigenous there, a remnant of the Marsupial-life of the tertiaries, or whether it may not have extended its range northwards from Central America in more recent times it is hard to say. Certain it is that the Virginian Opossum is very closely allied to its South American representative Didelphys azaræ, and by some authors is considered merely as a sub-species. Besides the Virginian Opossum five others of the same genus are registered by Alston as occurring within the boundaries of the Central American Sub-region. The remaining species of Didelphys are distributed all over South America down to Paraguay and La Plata, and one species at least occurs in Chili to the west of the Andes.
The Water Opossum (Chironectes) has likewise a wide distribution—from Guatemala to Southern Brazil, but it is absolutely restricted to the Neotropical Region.
SECTION V.—SUMMARY AND DEDUCTIONS Table of the genera of the Order Marsupialia, showing the distribution of the species.
FAMILY V. PEROMELIDÆ. 1. Perogale . . . . . 2 2. Peromeles . . . . 3. Cheropus . · :| 1
FAMILY VI. NOTORYCTIDÆ. 1. Notoryctes. ...:
DASYURIDÆ. 1. Thylacinus . . . . 2. Sarcophilus . . . . 3. Dasyurus . . . . 4. Phascologale. . . 5. Sminthopsis ... 6. Antechinomys .. 7. Myrmecobius. ..
Family VIII. 28 DIDELPHYIDÆ. 1. Didelphys . . . . . 25 2. Chironectes . . . . 1