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CHAPTER XIII

DISTRIBUTION OF THE CETACEANS AND

SIRENIANS

In a previous chapter on this subject (Chapter VIII., p. 197) I have already stated the principal facts known respecting the distribution of these two marine orders of mammals and need not now repeat them. But I append a list of the genera with the approximate numbers of the generally recognized species and some general indications of their ranges, and I add some general deductions.

Table of the genera of the Order Cetacea, showing the approximate number of valid species and their distribution.

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DEDUCTIONS

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 Delphinidæ, 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 (Platanistide) 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 Platanistidæ some of the Delphinidæ are found in rivers, such as Orcella fluminalis 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.

CHAPTER XIV

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.

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