2 4 8 THE MAMMALS OF THE NORTH ATLANTIC 



its whole vast length, although it seldom leaps into the air : when about to descend, 



the huge flukes are lifted high above the waves. Like the last, this species feeds 



on fish, especially pilchards and sprats, but also consumes minute crustaceans. 



In spring it journeys northwards, and resorts to the neighbourhood of the shores 



during the breeding-season, although it spends the winter in the open sea. 



The lesser fin- whale (B. rostrata), which has a pointed muzzle, and seldom 



exceeds about 33 feet in length, is characterised by a glistening white band across 



the upper part of the flipper, which contrasts conspicuously with the greyish 



black of the rest of the outer side of this appendage and the upper-parts generally. 



The under-parts, inclusive of the lower side of the flukes, are white. The species 



is further distinguished by having only eleven pairs of ribs, and the almost 



white whalebone. Inhabiting the northern seas of both hemispheres, it is specially 



common off" the coast of Norway, and is likewise by no means rare around the 



British Isles. It occurs in the Arctic Ocean, which it enters from the Pacific by 



way of Bering Strait. In the North Pacific it occasionally visits the estuaries of 



large rivers, as it does the fiords and bays of Norway in the other hemisphere. 



The fourth and last European member of the group is Rudolphi's fin-whale 



(B. borealis), which attains a length of about 50 feet, and has thirteen pairs of ribs. 



It may be distinguished from the last species by its smaller back-fin and the shorter 



flippers. In colour it is bluish black with long white spots above, and more or 



less white below, though the under sides of the flukes and flippers are black. The 



black whalebone is more curled and frayed at the ends than that of the other species, 



for, unlike it, this finner never eats fish, but feeds exclusively on small crustaceans. 



A very different animal is the hump-backed whale (Meqaptera 

 Humpback. J ... . P 



boops), another North Atlantic species, which attains a length of some 



50 feet, and is black above, and more or less marbled with white below. The 

 flippers are either white or spotted with white, and the species owes its name to the 

 presence of a protuberance on the hinder half of the back, which apparently varies 

 in height in different individuals. This hump carries a small back -fin, which, 

 together with the fluted pouch on the throat, indicates its relationship to the fin- 

 whales. From these it differs, however, by the comparatively large size of the warty 

 head, the greater depth of the body, and the excessive length of the flippers, which 

 measure from 10 to 12 feet in length, and have scalloped edges. The black 

 whalebone is short and thick. Humpbacks occur north and south of the equator 

 in both the Atlantic and the Pacific, and also in the Indian Ocean ; but some 

 naturalists regard the one inhabiting the Indian Ocean and the Persian Gulf as 

 distinct from the European form. 



The Atlantic black whale or right- whale (Balama biscayensis or glacialis) is 

 referred to in another chapter. 



