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1. The Order Cetacea contains from eighty to ninety known species, belonging to about forty-four genera and four families.
2. Cetaceans are found in all seas from the Equator to within the Arctic and Antarctic Circles, and in some of the larger rivers (the Ganges, Brahmaputra, Indus, and Irawadi in the Old World, and the Amazon and La Plata in the New).
3. The species of Oceanic Cetaceans are mostly very widely distributed, especially the Delphinidse, but in some cases are local, some species being confined to the Arctic and Antarctic Seas respectively, and some being peculiar to the Pacific and to the North Atlantic.
4. The Fluviatile Dolphins proper constitute a family of themselves (Platanistidm) with a very singular distribution, one genus being restricted to the rivers of India, and two others to those of South America.
5. Besides the Platanistidse some of the Delphinidse are found in rivers, such as Orcella flwtninalw in the Irawadi, and Sotalia tucuxi (with perhaps others of the same genus) in the Amazon.
6. None of the great lakes of any continent is known to be inhabited by Cetaceans.
DISTRIBUTION OF EDENTATE MAMMALS
Section I.—Introductory Remarks
As is the case with most ancient groups, we find the various types of Edentate Mammals strictly limited to certain localities on the earth's surface, so that the study of their distribution, especially when taken in connection with what we know of the extinct forms of the same group, comes to be a matter of much interest. In the present case, however, we propose to confine our remarks to the existing Edentates, as we are discussing the distribution of recent and not of fossil mammals, and merely to allude to the extinct forms when necessary.
As regards the existing Edentates, as has been well shown by one of our leading authorities on mammals, those of the Old World and those of the New are essentially distinct. The two Old World families commonly assigned to this order, are so different in important points of structure from the American families, that it may be even considered doubtful whether they were derived from the same primary branch of mammals. We will, therefore, take the two groups separately, and begin with the forms of the New World.
Section II.—Distribution Of The New World
The Edentates of the New World are at present represented by three families, the Sloths (BradypodicUe), the Ant-eaters (Myrmecophagidm), and the Armadilloes (Dasypodidm), all well distinguished from each other, although essentially modified on the same plan of structure, and more or less united together by other Edentates now extinct. All three families belong entirely to the Neotropical Eegion, although one of the Armadilloes appears to have intruded itself farther north than the generally recognized northern boundary of that Region.
Of the Sloths, two genera are well established—the Three-toed Sloths (Bradypus), with about five species, and the Two-toed Sloths (Cholopus), with two species. The Sloths are entirely arboreal in their habits, and are met with only in the dense forests of Central and Southern America, from Nicaragua down to Bolivia and Southern Brazil.
The Ant-eaters, of which three well-marked forms are known, belonging to so many genera, each with one species, have a somewhat wider distribution, being not absolutely confined to the tropical forests. The Great Ant-eater (Myrmecophaga jubata), extends as far north as Guatemala, and from Costa Rica southwards is found in suitable localities all through Venezuela, Guiana, and Brazil to Paraguay.
The Tamandua Ant-eater (Tamandua tetradactyla), which varies much in colour and markings, extends even farther north than its larger brother, as specimens have been obtained in Southern Mexico. Southwards it passes throughout South America as far as Paraguay, where Rengger assures us it is common, and widely distributed. The little Two-toed Ant-eater (Cyclothurm didactylus), a purely arboreal form, is also found in Guatemala, Nicaragua, and Costa Rica, but does not range so far south as the two former species, though it extends throughout the great Amazonian valley into Peru.
The Dasypodidm, or Armadilloes, which contain the third family of American Edentates, are more numerous and more diversified in their characters than the two preceding families. The eighteen or twenty species generally recognized by naturalists may be divided into four subfamilies and seven genera. The general area of their distribution is rather larger than that of the Sloths and Ant-eaters. One Armadillo, as has been already mentioned, goes as far north as Texas, and Armadilloes are found all over the Argentine Republic down to Patagonia.
The most remarkable of the Armadilloes, and one that must form a sub-family by itself, is the little Pichy-ciego of the Argentines (Chlamydaphorm truncatus), which is found in the sandy plains of the vicinity of Mendoza, and also, as has been recently ascertained, near Bahia Blanca in the eastern part of the Argentine Republic. A second species of this genus, more recently discovered (C. retusus) is met with in Bolivia.
The typical Dasypodime, consisting of about eleven or twelve species divided among four genera, are distributed all over the area of the family, south of Panama, but do not range into Central America, so far as has hitherto been ascertained.
The Giant Kangaroo (Priodon gigas), which belongs to