Online Encyclopedia

NORTHERN ZONE

Online Encyclopedia
Originally appearing in Volume V14, Page 270 of the 1911 Encyclopedia Britannica.
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NORTHERN ZONE.—The boundaries of the northern zone coincide in the main with the northern limit of the equatorial zone; but they overlap the latter at different points. This happens in Syria, as well as east of it, where the mixed faunae of the Jordan and the rivers of Mesopotamia demand the inclusion of this territory in the northern zone as well as in the equatorial; in the island of Formosa, where a Salmonid and several Japanese Cyprinids flourish; and in Central America, where a Lepidosteus, a Cyprinid (Sclerognathus meridionalis), and an Amiurus (A. meridionalis) represent the North American fauna in the midst of a host of tropical forms. There is no separate arctic zone for freshwater fishes; ichthyic life becomes extinct towards the pole wherever the fresh water remains frozen throughout the year, or thaws for a few weeks only; and the few fishes which extend into high latitudes belong to types in no wise differing from those of the more temperate south. The highest latitude at which fishes have been obtained is 82° N. lat., whence specimens of char (Salmo arcturus and Salmo naresii) have been brought back. The Palaearctic or Europaeo-Asiatic Region.—The western and southern boundaries of this region coincide with those of the northern zone. Bering Strait and the Kamchatka Sea have been conventionally taken as the boundary in the north, but the fishes of both coasts, so far as they are known, are not sufficiently distinct to be referred to two different regions. The Japanese islands exhibit a decided Palaearctic fish fauna with a slight influx of tropical forms in the south. In the east, as well as in the west, the distinction between the Europaeo-Asiatic and the North American regions disappears almost entirely as we advance farther towards the north. Finally, the Europaeo-Asiatic fauna mingles with African and Indian forms in Syria, Persia and Afghanistan. The boundaries of the North American or Nearctic region have been sufficiently indicated. The main features and the distribution of this fauna are identical with those of the preceding region.
End of Article: NORTHERN ZONE
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