« AnteriorContinuar »
(c) Summary and Deductions as regards the
FAMILY VI. PHYLLOSTOMIDE.
60. Chilonycteris .
76. Glossophaga 77. Phyllonycteris 78. Monophyllus. 79. Ischnoglossa
80. Lonchoglossa 81. Glossonycteris 82. Choronycteris
83. Lichonycteris. 84. Artibeus
85. Vampyrops 86. Chiroderma
87. Sternoderma 88. Ectophylla. 89. Ametrida
94. Desmodus 95. Diphylla
1. The Order of Chiroptera, or Bats, contains about 530 known species which are divided into ninety-five genera and six families.
2. They are found in every part of the world except within the Arctic and Antarctic Circles, and even in many islands where no other mammals occur.
3. The Fruit-bats (Pteropodidae) are met with only in the Old World, and mainly within the tropics.
4. The Vampires (Phyllostomatida) are entirely restricted to the Neotropical Region, except two or three species (out of eighty) which have passed over the boundaries into the Nearctic Region.
5. Two forms of the Vampires (Desmodus and Diphylla), having their dentition and digestive organs specially modified for that purpose, feed on the blood of living animals.
SECTION IV.-DISTRIBUTION OF RODENTS
Rodents are by far the most numerous of all the Orders of Mammals, comprising, according to a moderate calculation, nearly 1400 species which are arranged in 159 genera belonging to twenty-one distinct families. They are also among the most universally distributed of terrestrial mammals, being found in all latitudes high and low, and abundant in every part of the earth except Australia, where they are feebly represented by a few genera and species. The Rodents, especially the Mice (Murida), to which family rather more than half their number belong, are still imperfectly known; their arrangement and classi
fication have recently undergone important changes, and continual discoveries of new species and new alliances are made by several busy naturalists who are engaged mainly on a study of the smaller mammals. Under these circumstances it is hardly necessary for our present purpose to mention more than the names of most of the twenty-one families which constitute this complicated group, but we shall endeavour to pick out, as we go through them, some of the most noticeable facts connected with the distribution of these mammals.
Adopting Mr. Thomas's recent classification of the genera of this group1 (with a few slight deviations) as the best authority, we find the Anomaluridæ, a singular group of Flying-Squirrel-like Rodents, at the head of the Order. This family, with its three genera (Anomalurus, Idiurus, and Zenkerella), is purely Ethiopian, the eleven or twelve species which are referred to it occurring only in tropical Africa. Passing on to the next family, the Squirrels (Sciurida), we have an extensive group of about 240 species divided into eleven genera distributed nearly all over the earth's surface, with the exception of the Australian Region and Madagascar, where they are entirely deficient. The most numerous genus is that of the true Squirrels (Sciurus) which, subject to the exception just mentioned, is fairly distributed over the whole of the earth.
The Castoridæ, or Beavers, which come next, are represented in the present day only by the genus Castor, with two species, one of which occurs in the high latitudes of the Palearctic and the other in those of the Nearctic
"On the genera of Rodents," P. Z. S. 1896, p. 1012. Cf. Palmer, "Science," N. S., vi., p. 103 (1897).
Region. These two species are closely allied and perhaps scarcely distinguishable.
The Haplodontiidæ, or Sewellels, allied to the Squirrels, contain only the single genus Haplodontia, the species of which are confined to the Nearctic Region.
In the fourth family of the Rodents we meet with more familiar objects. The Gliridæ, or Dormice, with six genera and about nineteen or twenty species, have a curious distribution, being found only in the Ethiopian, Oriental, and Palearctic Regions. Each of these Regions, however, has its peculiar genera, true Glis and its allies belonging to the Palearctic Region, whilst Graphiurus is strictly Ethiopian, and the two remaining genera are restricted to the Oriental Region.
We now come to the Mice, or Muride, which, as already indicated, are exceedingly numerous and all-pervading creatures. Mr. Thomas places the 730 species of this family in seventy-eight genera. Mice are most numerous, perhaps, in the tropics, but are also well represented in Arctic latitudes, and in the shape of Lemmings (Lemmus), extend far towards the Pole.
They are not abundant in Australia proper, being represented there chiefly by the peculiar genus Hydromys and a few species of Mus. In Madagascar the seven genera of Muride met with are likewise altogether restricted to that anomalous island.
The Mole- rats (Spalacida), which follow next in Mr. Thomas's series, are a small and peculiar group, the members of which imitate the subterranean life of the Moles. The typical genus Spalax, with eight species, is confined to the Palearctic Region, whilst the Bamboo Rats (Rhizomys), represent the group in