« AnteriorContinuar »
doubt penetrated thus far from its ancestral abode in the Antarctic Ocean.
Returning to the central Atlantic we find two species of Seals inhabiting these waters, both belonging to the same genus, Monachus. One of these (AT. alhiventer) inhabits the Mediterranean and the adjoining coasts of the Atlantic,
while the other (M. tropicalis) is in these days restricted to some of the smaller and less known islands of the West Indies.
The Phocidm of the Antarctic Ocean all belong to genera distinct from the Arctic forms and more nearly allied to Monachus, the Seal of the Mid-Atlantic. They are of four species, belonging to as many genera: Ogmorhinus, Lobodon, Leptonychotes, and Ommatophoca. Besides these the Sea-elephant of the whalers (Macrorhinus) is essentially an Antarctic form, though now nearly extinct there, after
long persecution by man. But, as already noted, it extends. or has in former days extended, far up the west coast of America, and is still occasionally found on the coast of California.
Section III—Distribution Of Sirenians
Only two forms of Sirenians are at the present time existing on the earth's surface—the Manatee (Manatus)
Fig. 45.—The Dugong.
and the Dugong (Halicore)—each representing a distinct family of the Order. The Manatee (Fig. 44, p. 202) is an inhabitant of the coasts and estuaries of both sides of the middle Atlantic Ocean—one species (Manatus senegalensis) occurring on the African shores, and another (31. americanus) on the South American coast and in the Antilles. A third species (M. inunguis), so far as we know at present, is found only in fresh water high up the Amazon.
The Dugong (Halieore) (Fig. 45, p. 203) is distributed from East Africa, along the shores of the Indian Ocean and its islands, to North Australia. Three species of this genus have been established—Halieore tabernaculi from the Red Sea, H. dugong from the Indian Ocean, and H. australis from Australia; but it is doubtful how far these forms are actually distinguishable.
Besides Manatus and Halieore, a third quite distinct form of Sirenian was formerly an inhabitant of the North Pacific. This was Steller's Sea-cow (Rhytina stelleri), by far the largest animal of the group, which was exterminated by human agency about 1768. Fortunately recent researches in Behring's Island have been successful in supplying specimens of its skeleton for our principal museums, and Steller, its discoverer, left to posterity a good account of its habits and anatomy.
Section IV.—Distribution Of Cetaceans
Adopting the recognized division of the Cetaceans into two sub-orders, Mystacoceti and Odontoceti, according as to whether their mouths are furnished with baleen (" whalebone ") or teeth, we will first consider the True or Whalebone Whales, which consist of a single family Balaenidae, usually divided into five genera: Balama, Neobalmna, Rhachianectes, Megaptera, and Balmnoptera. Of these,
Balmna (Fig. 46, p. 204), Megaptera, and Balmnoptera are almost cosmopolitan—species of them, whether distinct or not is at present more or less uncertain, being met with in nearly every part of the ocean. But Rhachianectes has as yet been ascertained to occur only in the Northern Pacific, and Neobalmna in the South Polar Ocean, so that we have in these cases two well-marked local types to deal with.
The Toothed Whales (Odontoceti) are more diversified than the preceding group, and are usually held to embrace at least four existing families besides extinct forms.