MARINE MAMMALS 217 



and African coasts. The Manatee could hardly live to 

 cross the Atlantic. It is only found close to the coast, 

 in estuaries and rivers, where it browses on sea-weeds 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 (Monachus), 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. The hypothesis of a former barrier 

 of land between Africa and America, which we know is 

 supported by other facts of distribution, 1 would alone ex- 

 plain the difficulty. 



On the other hand, in the Pacific we find no such 

 break between the north and south. The aquatic mammals 

 of Notopelagia have evidently had free access to the whole 

 of the Pacific for a long period, and have well availed them- 

 selves of this facility. 



Again, while the great Southern Ocean exhibits a 

 considerable uniformity of marine mammalian life, we see 

 the Northern waters divided into two distinctly recogniz- 

 able Regions by the interposed masses of land. All these 

 facts, with the one exception of the supposed Atlantic 

 barrier, would tend in favour of the now generally ac- 

 cepted doctrine that the principal masses of land and 

 water are not of modern origin, but have existed mainly 

 in their present shapes throughout all ages. 



1 Cf. Wallace, Geogr. Distrib., vol. i., p. 156. 



