HIGH SCHOOL ZOOLOGY. 165 



Tlie general spindlo-shape of the body (Fig. HI), the hairless skin, 

 the thick layer of blubbci', the rudimentary cliaracter of the 

 olfactory organ, and the consequent restinction of the nostrils to 

 the respiratory function, the situation of the nostrils on the 

 top of the head, the conversion of the anterior extremities into 

 flippers (Fig. 110, D), the almost complete absence of the skeleton 

 of the posterior extremities, the peculiar horizontal caudal fin, and 

 the dorsal fin occasionally present, are all featui'es which are asso- 



Fig. 111. Outline of White Whale of St. Lawrence. (Beluga.) ^. 

 ciated with the conditions of their existence. The whales have 

 only one set of teeth, but these disappear in some of the mem- 

 l:)ors of tlie order, being replaced on the upper jaw by the horny 

 strainers (whalebone), which jirevent the escape of the minute 

 creatures on which the whalebone-whales live. Two groups of 

 Cetacea are therefoi'e distinguished — the toothed whales ami the 

 whalebone-whales. To the former belong the porpoises, (Fho- 

 cosna); dolpliins, [Delphimis); white whales, (^Beluga, Fig. Ill); 

 as well as the grampus (Orca) and the singular Narwhal (Mono- 

 don) ; they chiefly live on fish and cuttle-fish, for seizing which 

 they are provided with numerous sharp conical teeth, but the 

 Grampus has only a few very powerful and sharp teeth, in ac- 

 cordance with its habit of attacking the larger forms of its 

 own order, and the adult Narwhal is quite toothless, except for- 

 the single long spiral tusk of the male. 



Only the lower jaw is provided with teeth in the Spermaceti 

 whales (Catodon), whicli are chiefly remarkable for the 

 enormous liead swollen up by the accumulation of spermaceti 

 between the skull and the skin. 



