356 RORQUALS CHAP. 



symphysis of the jaws to the middle of the belly is, as in other 

 species, marked by furrows, forty to fifty-eight in number. The 

 hairy covering is reduced (in an adult female) to thirteen hairs 

 on each side of the lower jaw ; in a foetus there were also seven 

 hairs on each side of the upper jaw, as well as rather more on 

 the lower jaw altogether, forty-eight. This Whale appears to 

 feed chiefly upon small Crustacea, especially the Copepod, Calanus 

 finmarchicus. The number of baleen plates is about 330 on each 

 side of the jaw. This Whale sometimes swims singly, but usually 

 in schools of even as many as fifty. 



Rudolphi's Rorqual (B. lorealis) seems to be a perfectly 

 inoffensive beast ; it is said to be able to stay under water for 

 as long a time as twelve hours. 



A smaller species than the last is B. rostrata at the outside 

 33 feet in length. Here the hairy covering is reduced 1 to " two 

 small hairs on the integument covering the apex of the lower 

 maxilla." The colour is greyish black above, the underside 

 white. On the other hand, B. sibbaldii, the Blue Whale, is the 

 giant of its race, reaching a length of 85 feet. Its colour is a 

 dark bluish grey, with small whitish spots on the breast. The 

 dorsal fin is small and low with straight margins. 



B. musculus, the Finner, is intermediate in size not more 

 than 70 feet. It seems doubtful whether the " sulphur bottom," 

 B. australis, of Antarctica and B. pataclionica differ specifically 

 from this. 2 



The genus Megaptera is very near Balaenoptera, but differs 

 from it mainly in the following external and internal characters. 

 The dorsal fin is not very prominent, and its place is taken by a 

 lowish hump, whence, indeed, the common name of this Whale, 

 " Humpback." The pectoral fin is unusually long, and the 

 creature uses it to beat itself, the surrounding water, and, more 

 playfully, its mates. The general outline of this Cetacean is 

 more clumsy than that of Balaenoptera. The most important 

 internal difference is in the form of the scapula, which has at 

 most a slight acromion and coracoid process. These are rather 

 more pronounced, according to Messrs, van Beneden and Gervais, 3 



1 Perrin, "Notes on the Anatomy of B. rostrata," Proc. Zool. Soc. 1870, p. 805. 



2 von Haast, "Notes on a Skeleton of Balaenoptera australis," Proc. Zool. Soc. 

 1883, p. 592. 



3 Osteographie des Cttacte, Paris, 1880, p. 130. 



