214 THE GEOGRAPHY OF MAMMALS 



species {Macrorhinus angustirostris), but its differences 

 from the southern form (M. leoninus) seem to be but 

 trifling. 



As regards the Cetaceans of Mesirenia, our information 

 is at present very imperfect, and there is little to say except 

 that species of Megaptera, Balzenoptera, Physeter, Cogia, 

 and Ziphius certainly occur there, besides many repre- 

 sentatives of the widely spread Delphinidse. 



Section XL — The Southern Sea-region, or 



NOTOPELAGIA 



The wide ocean which surrounds the Southern Pole on 

 every side, and extends up to 40° S. lat., seems to present, 

 as regards its marine mammals, a nearly homogeneous 

 fauna, which we will now briefly consider. In the first 

 place it contains representatives of four genera of true 

 Phocidte — Ogmorhinus, Lobodon, Leptonychotes, and 

 Ommatophoca, which are peculiar to the southern seas, 

 and are quite distinct from all their northern representa- 

 tives in the Arctic Ocean. The Sea-elephant, Macrorhinus, 

 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 Macrorhinus, Otaria also, containing the group 

 of Eared Seals, appears to have been originally an Antarctic 

 group, and the greater number of its species are still found 

 in the Southern Ocean. But the Otarize have travelled 

 still further north than Macrorhinus, and three, if not 

 four, species are, as already stated, in these days well- 

 established inhabitants of Arctirenia. 



