Distribution of Marine Mammalia. 



273 



points in the general distribution of the marine Mammals, and 

 to their apparent significance. 



In the first place, it is evident that the Pacific has much more 

 in common with the Notopelagian region than the Atlantic. Otaria 

 and Macrorliinus, quite unknown in the Atlantic, extend themselves 

 to the northern extremity of the Pacific, the former pervading that 

 ocean up to Behring's Straits, and the latter reaching to the 

 Californian coast. It follows that in former ages there must have 

 been some barrier in the Atlantic which did not exist in the Pacific 

 to stop their progress northwards. The only barrier I can imagine 

 that would have efi'ected this must have been a land uniting South 

 America and Africa, across which they could not travel. Adoptino- 

 this hypothesis, we have at the same time an explanation of the 

 presence of the Manatee on both the American and African coasts. 

 The Manatee could hardly live to cross the Atlantic. It is only 

 found close to the coast, where it browses on seaweeds and other 

 vegetable food in shallow water. How did it travel from America 

 to Africa (or vice versa), unless there were a continuous shore-line 

 • between them ? The same may be said of the Monk-seal (Monachis), 

 of which one species lives in the Mediterranean and on the African 

 coast and islands, and another in the West Indies. We can hardly 

 believe that these creatures could easily traverse the whole Atlantic. 



ToPOMORPHS OF THE SeA-KEGIONS. 



I. Arotatlantis. 



HalicTioerus . 

 Cyatopliora. 



IV. Arctirenia. 

 Otaria. 



Hijperoodon. 



DelpMnnpterus. 



Monodon. 



II. Mesatlantis. 

 Monaclius. 



Manatus. 



Inia. 

 Fontoporia. 



III. Indopelagia. 

 JETalicore. 



Plantanisia. 



VI. Notopelagia. 



Ogmorliinus. 



Lobodon. 



LeptonycJiotes. 



OmmatopJioca. 



Otaria. 



Rhytina (extinct). 

 Bhachianectes. 



V. Mesirenia. 



Otaria. 

 Macrorhinus. 



Neobalcena. 

 Berardius. 



DECADE IV. — VOL. IV. — NO. TI. 



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