VIII. The Indian Sea-region, or Indopelagia.
The Marine Carnivora, so far as we know, are entirely foreign to Indopelagia, but the Sirenians are well represented by the Dugong, Halicore, which pervades all its northern coasts from North Australia to India and the Red Sea, and down the African coast to Lamu.[1] Whether the species of Halicore found at different points within this area are the same or different is still a matter of discussion, but there can be no doubt that Halicore is an exclusive inhabitant of Indopelagia. As regards the Whales of Indopelagia, we know that Physeter, Cogia, and Ziphius, and numerous forms of Delphinidæ, occur there; but I am not aware of any cetacean that is entirely restricted to this sea-region.
IX. The North Pacific Sea-region, or Arctirenia.
As was pointed out when speaking of Arctatlantis, Arctirenia has one genus of Phocidæ (Phoca) in common with the North Atlantic, and three of the species of this genus appear to be actually identical in these two sea-regions, whilst a fourth Phoca, P. fasciata, is only found in the North Pacific. The Walrus, Trichechus, is again a form of marine mammals common to both the great northern sea-regions. But the feature of Pinnipedian life that absolutely distinguishes Arctirenia from Arctatlantis is the presence in the former of three (if not four) well-marked species of the Eared Seals, Otariidæ, which are absolutely unknown in the vast extent of the Atlantic down at least to 30° S. lat.
Arctirenia has unfortunately lost its Sirenian, Steller's Seacow, Rhytina stelleri, the largest and finest modern representative of this formerly prevalent group, which since the days of the Pleistocene has greatly diminished in numbers; but I think we may still treat Rhytina as one of the characteristic forms of the Arctirenian sea-region. The North Pacific is also even at the present day the sole possessor of a remarkable genus of Whalebone Whales which combines the long head and elongate form of Balænoptera with the smooth skin of the throat and absence of the dorsal fin of Balæna.[2] This is the Grey Whale, Rhachia-
