356 MK. p. L. SCLATEB ON THB [Mar. 16, 



which, iu these days, is confined to the North Pacific, and does not 

 range farther south than the 20th parallel in that ocean. At the 

 same time it should be stated that indications have been discovered 

 that a nearly allied form existed iu the Atlantic in previous geo- 

 logical ages, though this is by no means certain. Besides Rhachia- 

 nectes, Balcena, Mcgaptei'u, and Balcenoptera are all represented in 

 the North Pacific, and also many species of Delpliinidte of which 

 little is at present known. But Rhi/tina and Bhachiaaectes are 

 the only genera of Marine Mammals absolutely confined to 

 Arctirenia. 



X. The Mid-Pacific Sea-region, or Mesirenia. 



The Eared Seals, Otaria, must have necessarily passed through 

 Mesirenia in their passage from south to north, though the only 

 record of their actual presence in the central part of the Pacific 

 is, so far as I know, the recent discovery of them in the 

 Gralapagos. It should be stated, however, that Tschudi records 

 the orcurrence of t\^o species of Otaria on the islands of the coast 

 of Peru, and that in 1802 Humboldt met with an Eared Seal on 

 the Island of San Lorenzo, in the Bay of Callao, which is only 

 some 12° south of the Equator. 



Like Otaria, the Sea-elephant (Macrorhinus) has apparently in 

 former ages travelled up the South American shores and estab- 

 lished itself as far north on the coast of California at about 34° 

 N. lat. The Californian Sea-elephant has been discriminated by 

 Gill as a distinct species {Macrorhinus angustirostris), but its 

 diff'erences 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 I have little to say except that species 

 of Mcgaptera, Balanioptera, Phi/seter, Cogia, and Ziphius certainly 

 occur there, besides many representatives of the widely spread 

 Deljjhinida. 



XI. The Southern Polar 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 Phocidce — Ogmorhinus, Lohodon, Leptonycliotes^, 

 and Ommafophoca, which are pecuhar to the southern seas, and are 

 quite distinct from all their northern representatives 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 



' This generic term, established by Gill in 1872, seems to take precedence 

 of Pceci!oj)/toca, proposed by Flower and Lydekker for the same type (L. wed' 

 delli) in 1S91. Cf. Allen, North American Pinnipeds, p. 418. 



