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Region only by a single species of armadillo (Tatusia novem-cincta), which almost certainly came up from the south, and is only met with just inside the southern borders.

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Among the Ungulates, the most remarkable form is the prong-buck (Antilocapra), which forms a distinct family of that order, and is entirely confined to this Region (Fig. 30, p. 156). It is allied in some respects to the Antelopes of the Old World, but it is unique among all the hollow-horned ruminants from the fact that it sheds its horns every year.

Two other genera, belonging to the family Bovidæ, are confined to the Nearctic Region; these are the Rocky Mountain goat (Haploceros), found only in the Rocky

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Mountains (Fig. 31, p. 157); and the Musk Ox (Ovibos), which ranges over the barren grounds at the extreme north of the continent, and spreads into Greenland (see Fig. 32). The latter, however, was also found in the northern parts of the Old World until a comparatively recent epoch, geologically speaking.

The Bisons (Fig. 33) are still common to the Nearctic and Palæarctic Region, though now nearly extinct in both hemispheres.

Rodents are very numerous in the Nearctic Region. According to the tables here used, which have been compiled from Flower and Lydekker's text-book of

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mammals, out of a total number of twenty-eight genera, thirteen are endemic. One of these, Haplodon, a small animal resembling the Prairie-dog in its habits, and found only west of the Rocky Mountains, forms a distinct family.

The Carnivora are also well represented, especially the genera of Cats, Dogs, Bears, and Weasels, all of which, however, are widely spread. The only endemic genus is that formed for the reception of the American Badger (Taxidea), which differs from its European ally in certain anatomical features.

In contradistinction to the Neotropical Region, the Insectivora are abundant in the Nearctic; there are no less

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than four genera of Moles met with, three of which are peculiar.

Amongst them is the remarkable Star-nosed Mole (Condylura cristata) which carries a ring of riband-like appendages at the end of its snout. These serve, no doubt, as a sensitive organ (see Fig. 34).

Finally, the Bats are neither very numerous nor of great importance; only one genus (Antrozous), containing one species, being peculiar out of a total of nine.

Summarizing, therefore, we find the Nearctic Region to be characterized by the exclusive possession of only two families of Mammals—namely, Antilocapridæ (the Prongbucks) and Haplodontidæ (the Haplodonts), and by the presence of sixty-six genera, of which twenty-one are restricted within its boundaries. On the other hand, in addition to the two orders already mentioned, Monotremes and Primates, the following important families are absent in the Nearctic Region, although fairly well spread over the Old World:

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That some of these families did, however, at one time exist on the North American continent has been shown by recent palæontological discoveries.

SECTION III.—SUB-DIVISION OF THE NEARCTIC REGION

The recent work of American naturalists, more especially that of Merriam (2) and of Allen (1), has greatly increased our knowledge of the mammals of North America and of their distribution. These naturalists have further shown that the Sub-regions adopted by Wallace in his well-known text-book on geographical distribution are not altogether supported by the facts now known to us.

Mr. Allen, in his paper on the distribution of North

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