1897.] DISTEIETJTION OF MARIXE MAMMALS. 357 



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

 greater number of its species, although no\v-a-days very much 

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

 the Otarice 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. 



The Sirenians are absent from Notopelagia, but Cetaceans of 

 every kind are abundant. Besides one or more representatives 

 of the true Whalebone Whale (Balcma), Xotopelagia has a 

 smaller representative of the group (Neohalcena) entirely restricted 

 to its area. It has also representatives of Megaptera and Balmio- 

 ptera, 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, Berardivs, restricted to the Xotopelagian area, while Ziplims 

 and Mesoplodon also occur there. The Dolphins {DeJjphinidce) are 

 likewise numerous, and present some distinct species, bat not, so 

 far as our present knowledge extends, auy 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 conveniently divided 

 into six Sea-regions, which, as marked in the chart now exhibited 

 (Plate XXIV.), are as follows :— 



I. Eegio Aectatlantica, characterized by its Seals (PJiocince), 

 of which two genera, Haliclinenis and Gystophora, 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 Mesatlais-tica, sole possessor of the Monk-Seal, 

 Monachus, amongst the Pinnipeds, and of the Sirenian genus 

 Manatus. 



III. Eegio Indopelagica, characterized by the presence of the 

 Sirenian Balicore and by the absence of Pinnipeds. 



IV._ Eegio Abctire^jica, with Phoca like the Eegio Ai-ct- 

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

 Sirenian Rhytina and of the endemic Cetacean Rhachianectes . 



V. Eegio Mesieexica, without true Seals {Phocince), but having 

 Otaria and Macrorhinus from the south ; no Sirenian known. 



VI. Eegio Xotopelagtca, characterized bv four endemic genera 

 of Phocidce, and by the presence of many Otarice ; without 

 Sirenians, but with two endemic forms of Cetaceans {Mobcdcena 

 and Berardius), 



