42 
CETACEANS 
the females both tusks remain in a similar rudimentary condition. The developed 
tusk of the male is composed 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 7 to 8 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 
A SCHOOL OF NARWHALS (jV, liat. size). 
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 rudiments—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 characterised by their blunt and rounded heads, in which the muzzle 
shows no sign of being produced into a beak. A special character of the animal is. 
to be found in the absence of a back-fin, which is represented merely by a low and 
