226 THE ZOOLOGIST. 



tatives of four genera of true Phocidce: Ogmorkinus,Lobodon,Lepto- 

 nychotes* and Ommatophoca, which are peculiar to the southern 

 seas, and are quite distinct from all their northern representatives in 

 the Arctic Ocean. The Sea-elephant, Macrorldnus, is also a denizen 

 of Notopelagia, though, as we have already seen, it has wandered 

 north along the South American coast far into Mesirenia. 



Like Macrorhinas, Otaria also, containing the group of Eared 

 Seals, appears to have been originally an Antarctic group, and 

 the greater number of its species, although nowadays very 

 much reduced in numbers, are still found in the Southern Ocean. 

 But the Otaria have travelled still further north -than Macro- 

 rhinas, and three, if not four, species, as already stated, are in 

 these days well established inhabitants of Arctirenia. 



The Sirenians are absent from Notopelagia, but Cetaceans of 

 every kind are abundant. Besides one or more representatives 

 of the true Whalebone Whale, Balcena, Notopelagia has a smaller 

 representative of the group, Neobalcena, entirely restricted to its 

 area. It has also representatives of Megaptera and Balcenoptera, 

 though it is doubtful how far they are even specifically distinct 

 from some of their northern representatives. 



Among the Toothed Whales, Odontoceti, we find a large 

 Ziphioid form, Berardius, restricted to the Notopelagian area, 

 while Ziphius and Mesoplodon also occur there. The Dolphins, 

 Delpldnidce, are likewise numerous, and present some distinct 

 species, but not, so far as our present knowledge extends, any 

 generic forms that do not occur elsewhere. 



But Notopelagia is sufficiently distinguished from all the five 

 more northern sea-regions by possessing four genera of Seals and 

 two of Cetaceans entirely restricted to its area. 



XII. Conclusions. 



It has therefore, I think, been shown that for the geography of 

 marine mammals, the ocean may be most conveniently divided 

 into six Sea-regions, which are as follows : — 



I. Reoio Arctatlantica, characterized by its Seals, Phocince, 

 of which two genera, Halicheerus and Cystophora, are peculiar, 



* This generic term, established by Gill in 1872, seems to take prece- 

 dence of Pcccilophoca, proposed by Flower and Lydekker for the same type, 

 L. iveddelli, in 1891. Cf. Allen, ' North American Pinnipeds,' p. 418. 



