Beginning with the Otariidæ or Eared Seals, commonly known as Sea-lions and Sea-bears, we find the greater number of the species confined to the South Polar Ocean, where they pass most of their time at sea, but, as is well known, resort to the land at certain seasons for breeding purposes. In the Atlantic Ocean, so far as I know, the Eared Seals have never been ascertained to occur further north than the estuary of the La Plata on the American coast, and the vicinity of the Cape on the African coast. But in the Pacific, on the contrary, three distinct species of Otaria are found all over the arctic portion of that ocean, and there are well-founded traditions of Eared Seals having been formerly met with in the Galapagos, while they still occur on the coasts of Peru and Chili. I think therefore we may assume that Otaria was originally an Antarctic form, but has travelled northwards along the West American coast and is now firmly established in the North Pacific. In a parallel way in the class of birds, the Albatrosses, Diomedea, which are 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, Trichechidæ, are entirely Arctic in their distribution; one species, Trichechus rosmarus, being peculiar to the North Atlantic, while 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, Phocidæ, 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 inhabiting various parts of this area, and the Grey Seal, Halichœrus, 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 up here thus far from its ancestral abode in the Antarctic Ocean.
Returning to the Central Atlantic, we find two species of Seals
