WHALEBONE WHALES. 
117 
pointed tusk, with the surface marked by spiral grooves and ridges. 
In some very rare cases both teeth are fully developed, as in the 
line skull exhibited near the skeleton. The Narwhal inhabits the 
Arctic regions, where it is tolerably abundant and gregarious, 
feeding on various species of cephalopods, small fish, and crusta- 
ceans. The use to which it puts its tusk (often erroneously 
spoken of as a ^^horn^^) is not known. 
Besides the adult skeletons and tusks exhibited on the left side 
of the gallery there is the skeleton of a foetal specimen in the wall- 
case near the door. In this specimen the two tusks are of equal 
dimensions, and two of the other small deciduous teeth are still 
in place. 
Suborder II. M y s t a c o c e t i, or Bal^noidea. 
Although the so-called \¥halebone Whales have rudimentary 
teeth developed at an early period of life, these soon disappear, and 
their place is occupied in the upper jaw by the baleen or whale- 
bone."’^ This consists of a series of flattened, horny plates, between 
three and four hundred in number on each side of the mouth. 
They are placed transversely to the long axis of the mouth, with 
very small interspaces between them. Each plate or blade is some- 
what triangular in form, with the base attached to the palate, and 
the point hanging downwards. The outer edge of the blade is 
hard and smooth, but the inner edge and apex fray out into long 
bristly flbres, so that the roof of the Whale’s mouth looks as if 
covered with hair, as described by Aristotle. The blades are 
longest near the middle of the series, and gradually diminish 
towards the front and back of the mouth. Baleen (as seen in 
various specimens in the Table-Case near the further end of the 
room) varies much in colour in dififerent species of Whales. In 
some it is almost jet-black, in others slate-colour, horn-colour, 
yellow, or even creamy white. In some the blades are variegated 
with longitudinal stripes of different hues. It differs also greatly 
in other respects, being short, thick, coarse, and stiff in some, and 
greatly elongated and highly elastic in those species (as the Green- 
land Whale, Balana mysticetus) in which it has attained its fullest 
development. Its use is to strain the water from the small marine 
mollusks, crustaceans, or fish upon wEich the Whales subsist. In 
