272 Notices of Memoirs— Dr. P. L. Sclater — 



which are peculiar to the southern seas, and are quite distinct from 

 all their northern representatives in the Arctic Ocean. The Sea- 

 elephant, Macrorhinns, 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 Macrorhinns, 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. Bat 

 the OtaricB have travelled still further north than Macrorkinus, 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 {Balcsna), Notopelagia has a smaller repre- 

 sentative of the group {Neohal(Bna) entirely restricted to its area. 

 It has also representatives of Megaptera and Balcsnoptera, 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, Jierardius, restricted to the Notopelagian area, while Ziphius 

 and Mesoplodon also occur there. The Dolphins (Delphinidee) 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, as follows : — 



I. Eegio Arctatlantica, characterized by its Seals (Phocinas), of 

 which two genera, HalichcBrus and Cystophora, are peculiar, whilst 

 Phoca is common to it and Arctirenia ; by the absence of Sirenians ; 

 and by the possession of three peculiar genera of Cetaceans 

 (Hyperoodon, Delphinapterus, and Monodon). 



II. Eegio Mesatlantica, sole possessor of the Monk-seal, Monaclius, 

 amongst the Pinnipeds, and of the Sirenian genus Manatus. 



III. Eegio Indopelagica, characterized by the presence of the 

 Sirenian Halicore and by the absence of Pinnipeds. 



IV. Eegio Arctirenica, with Phoca like the Eegio Arctatlantica, 

 but having Otaria also ; the home of the (now extinct) Sirenian 

 Bhytina and of the endemic Cetacean Bhachianectes. 



V. Eegio Mesirenica, without true Seals (Phocinee), but having 

 Otarice and Macrorhinns from the South ; no Sirenian known. 



YI. Eegio Notopelagica, characterized by four endemic genera 

 of Phocidge, and by the presence of many Otaria ; without 

 Sirenians, but with two endemic forms of Cetaceans [Neobalcena 

 and Berardius). 



In conclusion, I will call attention to some of the more remarkable 



