70 WHALEBONE AND WHALEBONE WHALES. 



members of this group are more specialized than their 

 toothed cousins, in regard to the structure of the skull in 

 the region of the nose and the retention of an organ of 

 smell, as well as in the double apertures of the nostrils, 

 they depart less widely from the ordinary mammalian 

 type. And it is from this evidence that zoologists regard 

 the two main groups of whales as being widely divergent 

 branches from a common ancestral stock, if, indeed, they 

 do not go so far as to consider that each has had a totally 

 independent origin. 



With regard to the number of forms by which they are 

 represented, the whalebone whales are far less numerous 

 than the toothed group, the whole of them being included 

 within a single family. What the group lacks in number 

 is, however, amply made up by the great bodily size of 

 its various representatives. Among the toothed whales, 

 the sperm-whale alone attains gigantic dimensions ; 

 whereas in the present group there are several species, 

 such as the Greenland whale, which nearly equal that 

 enormous creature in bulk, while two of the rorquals far 

 surpass it. This, however, is by no means all, for whereas 

 the great majority of the dolphins and porpoises are 

 relatively small cetaceans of less than twenty feet in 

 length, the smallest member of the present group is the 

 southern pigmy whale, which attains a length of twenty 

 feet, while next to this comes the lesser rorqual, whose 

 length is frequently close on thirty feet. 



Of the various genera of this group, the most specialized 

 are the typical or right whales {Brihrna), in which the 

 black whalebone is far longer and more elastic than in any 

 of the others, except the pigmy whale ; while, in order to 

 accommodate it in the moiith, the skull has the 

 palate narrower and much more highly arched, and 

 the two branches of the lower jaw more outwardly 

 bowed than in the other members of the group. Ex- 

 ternally, these whales — which are commercially of far 

 greater value than the undermentioned rorquals — are 

 characterized by the inordinately large dimensions of the 

 head, by the smooth throat, the moderate length of the 

 flippers, and the total want of a back-fin. So gigantic 



