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 

 fine 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^ENOIDEA. 



Although the so-called te Whalebone 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 ft 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 fibres, 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 different 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, Balaena 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 which the Whales subsist. In 



