142 WILD BEASTS OF THE WORLD 



true fish, of the various flat-fishes. The animal's mouth is not only 

 practically toothless, but small, and it is a puzzle when it is found to- 

 have swallowed, in sections, a Skate larger than the diameter of the 

 mouth, unless it had picked this up in fragments, some other animal 

 having done the biting. That the tusk is put to some use appears 

 from the fact that the point is always clean, the base being encrusted 

 with a greasy substance. 



Little, however, is known about the habits of this strange creature, 

 though its " horn " has been a familiar curiosity for many centuries, 

 and was that assigned to the Unicorn of fable ; it still has some value. 



THE WHALEBONE WHALES 



THE Narhwal is the most nearly toothless of the Dolphins, though 

 not so quite short of teeth as the Beaked Whales ; but there is an 

 important section of the Cetaceans which have no teeth at all the 

 Mystacoceti, or Whalebone Whales. The Whalebone, or " baleen," 

 which takes the place of teeth, hangs from the sides of the upper jaw 

 in long parallel slips, whose inside edges fray out like hairs ; it is, 

 in spite of its name, a horny, not a bony substance. The use of the 

 ranges of baleen plates is to strain off the water when these Whales 

 feed ; they all have very large mouths, though their throats are narrow, 

 and feed on sea-animals which swim in shoals, gulping in great 

 mouthfuls of the life-laden brine, and then letting the water drain off 

 at the sides of the mouth, leaving the hapless victims stranded on the 

 great tongue. A humble miniature repetition of this performance may 

 be seen in the Common Duck's way of feeding, and in the wild 

 Shoveller Duck (Spatula clypeatd), the straining plates of the bill are, 

 as Darwin has pointed out in one of the most interesting sections of 

 his great work, a very fair reproduction of whalebone on a small 

 scale, various other Ducks showing graduating approaches to the 

 Shoveller's perfected arrangement. 



