ANTARCTIC ZOOGEOGRAPHY 377 



foregoing species of seals and the two essentially Antarctic species 

 of penguins. On the one hand the Adelie penguin and the crab- 

 eater seal select the same pelagic environment, keeping in touch with 

 raft and floe ice and feeding upon plankton crustaceans; on the other 

 the emperor penguin and the Weddell seal are littoral and non-migra- 

 tory, always remaining as far south as the existence of ice seams or 

 leads of open water will permit. The food of both is fish. Their 

 choice of habitat protects them from enemies, the Weddell seal being 

 as free from the attacks of the killer whale as the emperor penguin is 

 from the depredations of the skua. 



The sea leopard, which is more or less of a hermit seal, has an 

 exceedingly broad latitudinal range, being found from the shores of 

 the Antarctic Continent northward even to parts of the temperate 

 zone. Fish, cephalopods, young seals of other species, diving petrels, 

 and cormorants have been found within the stomachs of sea leopards, 

 but the primary food of the creature throughout its range is pen- 

 guins. In its amazingly formidable dentition, in speed and ferocity, 

 and in certain unique specializations of its internal anatomy^^ it is 

 built as an impressive engine of destruction to the birds which form 

 its prey. 



Finally the Ross seal, the rarest of the quartet, is confined to 

 southerly parts of the area, being unknown to the northward of the 

 pack ice. Its dentition is feeble, the cheek teeth being degenerate, 

 but the incisors and canines have curved needle-like points with which 

 this seal seizes the soft cephalopods that form its food. 



In the geographic arrangement of Andersson,^° referred to above, 

 the Antarctic and sub-Antarctic seals and sea bears are grouped as 

 follows, except for one slight modification here made: 



1. Circumpolar and exclusively Antarctic — Ross seal. 



2. Circumpolar in the Antarctic but occasionally reaching sub- 

 Antarctic latitudes in the American quadrant — Weddell seal and 

 crab-eater seal. 



3. Circumpolar throughout both the Antarctic and sub-Ant- 

 arctic — sea leopard. 



4. Circumpolar in the sub-Antarctic and penetrating into the 

 Antarctic by way of the South Shetland-South Orkney-Palmer Land 

 route — sea elephant {Mirounga leonina) and fur seal {Arctocephalus 

 australis) and perhaps other closely related species or races. 



Sea elephants and fur seals have been observed but rarely in the 

 pack ice. Both were formerly exceedingly abundant upon the whole 

 chain of sub-Antarctic islands, extending southward at least oc- 



" R. C. Murphy: The Trachea of Ogmorhinus, With Notes on Other Soft Parts, Bull. Amer. 

 Museum of Nat. Hist., Vol. 32, 1913, pp. 505-506. 

 M Work cited in footnote 31, above. 



