1214 THE CETACEANS 



less exclusively fresh water. They have been divided into a considerable number 

 of genera, but many of these are very closely allied, and mainly distinguished by 

 differences in the skeleton. 



THE NARWHAL 

 Genus Monodon 



The strange-looking animal commonly known as the narwhal {Monodon monoceros) 

 differs from all other members of the family by the enormous spirally-twisted tusk pro- 

 jecting from one side of the upper jaw of the male. This tusk is nearly always that 

 of the left side, its fellow on the opposite side being only a few inches in length, and 

 lying entirely concealed within the bone of the jaw, while in the females both tusks 

 remain in a similar rudimentary condition. The developed tusk of the male is com- 

 posed solely of ivory, and its spiral twist always runs from left to right. In form it 

 is cylindrical, and tapers more or less markedly from root to tip. Not unfrequently 

 the tusk attains a length of from seven to eight feet, or more than half that of 

 the entire animal. Very rarely narwhals are met with in which the right tusk is 

 developed as well as the left, but there appears to be no known instance of the right 

 tusk being developed while the left remains rudimentary; and it is noteworthy that 

 when the right tusk is developed it has the same left-to-right twist as its fellow. 

 A fine narwhal's skull with two tusks is preserved in the Cambridge Museum. Apart 

 from a few small, rudimentary ones, which are irregular in their occurrence, the male 

 narwhal has no teeth except the tusk, while the female save for similar rudi- 

 ments is toothless. 



Although the presence of the tusk in the male narwhal, and the practically 

 toothless condition of the female, are alone sufficient to distinguish the genus from 

 all other dolphins, it is necessary to say something further regarding the form and 

 structure of this singular animal. In the first place, the narwhal belongs to a group 

 of dolphins characterized by their blunt and rounded heads, in which the muzzle 

 shows no sign of being produced into a beak. A special characteristic of the animal 

 is to be found in the absence of a back fin, which is represented merely by a low and 

 ill-defined ridge. The flippers are short, wide, and rounded. In color the narwhal 

 is dark gray or dusky above and white beneath, the back and sides being irregularly 

 mottled with various shades of gray. The entire length may vary from twelve to 

 about sixteen feet. A tusk measuring eight feet in length had a basal girth of 

 seven and one-half inches. 



The narwhal resembles the Greenland whale in being an inhabitant 

 Distribution **.*. j -i_ ... ... . . . ,. . 



of the icy polar seas, and like that species is circumpolar in its distri- 

 bution; it is, however, apparently local in its range, being, according to Captain 

 Scammon, but rarely found in the seas accessible to the whalers who pass through 

 the Behring Strait. Although seldom occurring to the south of the sixty-fifth parallel 

 of north latitude, there are three instances (one in 1648, a second in 1800, and a 

 third eight years later) of narwhals visiting the British coasts. From the extreme 

 rarity of such occurrences, there is, however, no doubt that the individuals in ques- 



