THE IMPENETRABLE SEA 



rorqual. The right whales are heavy and compact in 

 form, and are built for cruising about slowly in search of 

 the small floating invertebrates which are their main 

 food. The humpbacks are bulky but uncouth — heads 

 broad and rounded in front but flat on top, with rows of 

 hemispherical tubercles — they can attain a fair speed, 

 due to the length of their flippers. 



The finners, or rorquals, which are built for speed, and 

 which prey largely on fish which they have to chase and 

 catch, are the ocean greyhounds of the baleen whales. 

 Their bodies are long and streamlined, and their necks 

 partially mobile. The typical finback — the most com- 

 monly observed and best known of the finners — ranks 

 next in size to the blue whale. Its shape is extremely 

 attenuated. The adult individuals sometimes reach a 

 length of eighty feet. Finbacks are remarkable for their 

 assymmetrical coloration: the whale's back is grey, 

 striped longitudinally with white, and the lower jaw is 

 also white on one side only. 



The sperm whale {Physeter macrocephalus) is a member 

 of the toothed whales (Odontoceti), the second division of 

 the Cetacea, and the division which comprises porpoises, 

 dolphins (including the killer whales), and bottlenosed 

 or beaked whales. 



Fully grown the sperm whale reaches a length of sixty 

 feet. The female is much smaller. 



The head of the sperm whale is immense, although all 

 whales do not have large heads in proportion to their 

 bodies. It is shaped like a great elongated wedge, with 

 the thicker end uppermost and the edges and smaller end 

 rounded. The blowhole is single and situated at the end 

 of the snout on the left side, and the lower jaw is very 

 narrow and much shorter than the upper. The two sides 

 of the lower jaw are joined together anteriorly for about 

 one-half the length. It has rudimentary upper teeth. The 

 lower ones (forty-four in number and cone-shaped) fit 

 into pits in the upper jaw when the mouth is closed. The 



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