the Albatrosses (Diomedea), which is essentially a group of the Antarctic Seas, are represented by three distinct species in the North Pacific.

The second family of the marine Carnivora, on the other hand, the Walruses (Trichechida), are entirely Arctic in their distribution-one species (Trichechus rosmarus)

(see Fig. 42, p. 200) being peculiar to the North Atlantic, a second nearly allied species (T. obesus) takes its place in the Northern Pacific.

The third family of Pinnipeds is more numerous and varied, both in genera and species, than the two preceding, and has a more extended range. The Seals, Phocida,

embracing about nine different generic forms, are most numerous in the Arctic and Antarctic Seas, but are also feebly represented in some intermediate localities. Beginning with the North Atlantic, we find several species of Phoca (Fig. 43, p. 201), inhabiting various parts of this area, and the Grey Seal (Halichorus) and the Bladder-Seal

(Cystophora) exclusively confined to it. In the North Pacific all the four true Seals belong to the genus Phoca, and three of them are identical with the North Atlantic species; but when we descend as far south as the Gulf of California on the American coast we meet with a species of Sea-elephant (Macrorhinus) which, like Otaria, has no

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 (M. albiventer) 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 Phocide 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)

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 (M. ameri