284 WHALES AND DOLPHINS 



Sub-family Delphinapterin^e. 



In all but two genera at least the first two neck vertebrae 

 are fused together ; the two exceptions are the Narwhal and 

 the White Whale, which have been placed together in a sub- 

 family, the Delphinapterinae, whilst the sub-family Delphininae 

 embraces all the remaining genera. 



Genus Monodon. 

 THE NARWHAL {Monodon monoceros). PI. VII c. 



The Narwhal with its " unicorn " tusk is so well known that 

 description is hardly necessary. The greatly elongated 

 spirally twisted tooth in the male extending outwards from the 

 front of the head is the most distinctive feature of this species. 

 In adult animals of both sexes a single pair of teeth is developed 

 in the upper jaw, but in the female both teeth usually remain 

 embedded in the bone of the jaw and concealed throughout 

 life, whereas in the male the right tooth is normally hidden, 

 whilst the left grows outward to a length which may exceed 

 9 feet and is not infrequently more than 8 feet. Occasionally 

 both tusks are elongated to the same extent, but even in 

 such instances the right-handed spiral persists in each tusk. 

 Infrequently also the left tusk may be elongated in the 

 female animal, and again in the male the right instead of 

 the left may be the conspicuous one. 



The head of the Narwhal is comparatively small and is 

 evenly rounded ; the snout is not drawn out into a beak or 

 rostrum. There is no dorsal fin, but in its place a low ridge, 

 an inch or two in height, extends from 2 to 3 feet along the 

 back about midway between the tip of the snout and the tail. 

 The flippers are small, broad in proportion to their length, and 

 bluntly rounded. 



The young of this species, bluish-grey in colour, are darker 

 than the adults and do not have the mottling assumed later in 

 life. The older animals are grey-white with dark grey or 

 blackish spots on the back, becoming lighter in colour on the 

 sides and belly. A good deal of individual variation occurs 

 and some old animals may be almost entirely white. 



