(c) Summary and Deductions as regards the Table of the genera of Bats, showing the approximate number of species found in each of the six Regions. (c) Summary and Deductions as regards the FAMILY VI. 60. Chilonycteris . 64. Macrophyllum 68. Glyphonycteris 75. Rhinophylla 87. Sternoderma 92. Brachyphylla. 93. Centurio 94. Desmodus 95. Diphylla ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... DEDUCTIONS 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 (Pteropodide) 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 (Muridæ), 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 (Anoma- · lurus, 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). |