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CHAPTER XV

DISTRIBUTION OF MARSUPIALS AND

MONOTREMES

SECTION I.-INTRODUCTORY REMARKS

The distribution of the two lowest orders of mammals, at which we have now arrived, is a comparatively simple matter, as these primitive creatures, which, according to the views of the highest authorities, form two primary subclasses of the whole class of Mammals (Metatheria and Prototheria), are confined exclusively to two of the great Zoological Regions of the earth. We will, nevertheless, pass the different families and the principal genera of these two orders in short review, and endeavour to point out the principal known facts of their distribution.

SECTION II.-DISTRIBUTION OF THE MARSUPIALS

The Marsupials have, until recently, been classified in six families, five of which belong to the Australian and one only to the Neotropical Region, and such was the plan of arrangement adopted for them by Mr. Thomas in his excellent catalogue of this group of mammals published in 1888. But great discoveries in this class have been made during the past ten years. A new Marsupial, of a most remarkable form of structure, necessitating the formation of a new family, has been found in Australia, and Mr. Thomas himself has shown the necessity of adding to the Neotropical section a Marsupial which is more allied to the Australian forms than to those previously known from America, and which necessitates the creation of a second Neotropical family. We have now, therefore, to deal with eight families of Marsupials, six of which belong to the Australian Region and two to America. These families embrace altogether about 172 species, of which 144 are Australian and 28 are American. According to Mr. Thomas's arrangement, these are divisible into two large groups, the Diprotodonts, which are mostly vegetable-eating animals, and the Polyprotodonts, which feed generally on flesh and insects.

SECTION III.- DISTRIBUTION OF DIPROTODONT

MARSUPIALS

The Kangaroos, or Macropodida, which form the first family of the Diprotodont section, are a numerous group embracing altogether more than sixty known species. These are distributed all over the Australian Region, but are specially abundant in Australia, where, as is well known, the Kangaroos form one of the most striking features of its peculiar mammal-life. In New Guinea and the Papuan Islands Kangaroos are by no means so abundant, especially those of the genus Macropus and the larger allied forms. On the other hand Dorcopsis and other smaller forms of Kangaroos range through the Papuan Sub-region up to Wallace's line, and New Guinea is especially peculiar for its Tree-kangaroos (Dendrolagus), although this genus likewise occurs in the tropical forests of Northern Queensland.

The second family of Diprotodont Marsupials—the Phalangers (Phalangerida) is likewise diffused over the whole Australian Region, and has even crossed the dividing line into Celebes, which, as already shown, must be included in the Oriental Region in spite of its possessing this single Marsupial form. This family contains some thirty-five species divided into twelve genera.

The typical genus Phalanger is a characteristic form of the Papuan Subregion, and only touches Australia at its northern extremity. It is of this genus that two species (P. ursinus and P. celebensis) occur in Celebes, to which island and the adjacent Sanghir Islands, so far as is at present known, they are restricted. Two of the genera of this family are so distinct from the remainder as to be generally assigned the rank of sub-families of themselves. These are the curious little Tarsipes, restricted to Western Australia, and the Koala, or native Bear (Phascolarctus), which is widely distributed in Eastern Australia but does not occur outside of it.

Next to the Phalangers we must, I suppose, place the new family of American Marsupials called by Mr. Thomas Epanorthidæ, as he refers the single genus yet known of it to the extinct Epanorthide of Ameghino, which he considers ought to include the recent as well as the fossil members of that nearly extinct group. According to Mr. Thomas the Neotropical Cænolestes is clearly a Diprotodont Marsupial, as not only does it possess the characteristic development of the lower incisors, but even its molar teeth resemble most closely in structure those of certain members of the Australian family Phalangeridæ.

Of Cænolestes

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

MARSUPIALS

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 (Chæropus) which is restricted to the Australian continent.

Between the Peromelida and the Dasyuridæ 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 extra

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ordinary 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 Canidæ. 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 Dasyuridæ 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,

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