162 THE DISTRIBUTION OF 
eating seal (Lobodon carcinophaga), the sea-leopard 
(Stenorhynchus leptonyx), which all occur in the region 
of ice-pack, while the sea-elephant (Macrorhinus leo- 
ninus), and the southern fur-seal (Otaria jubata) occur 
in sub-Antarctic seas as well as elsewhere. The fact 
that all these different kinds of seals tend to occur in 
cold regions cannot be ascribed wholly to deliberate 
choice on their part, for the young of all are born on 
the land, and the animals seek out places as free as 
possible from molestation, which are more frequent in 
polar seas than elsewhere. Since man joined their 
enemies many species are being driven further and 
further back into the inaccessible parts of the polar 
seas, or have been virtually exterminated. 
The seals, walrus, and sea-otter, the last named 
being a fur-bearing animal found off rocky coasts in 
the North Pacific, are all carnivores which have taken 
recently to the aquatic life, and are still bound to 
terra firma at the breeding season. There are, how- 
ever, two orders of mammals whose members are 
entirely aquatic, their young being born under water. 
These are the Cetacea or whales and dolphins, and 
the Sirenia or sea-cows. The former are powerful 
swimmers, and are pelagic. Their only connexion with 
shore is that the greater abundance of fish in shallow 
water brings many of them to the vicinity of sub- 
marine ‘banks’, while the whalebone whales haunt 
relatively shallow water in high latitudes, because of 
the abundance of small marine organisms there. 
The Sirenia include only two living animals, the 
dugong (Halicore) found in the Pacific and Indian 
Oceans, and extending southwards to the shores of 
Australia, and the manatee (Manatus) which lives in 
the estuaries of the great rivers which flow into the 
