80 



NUTRITION. 



long, flexible, horny plates or fans, fringed at the margin, 

 which serve as strainers to separate the minute marine ani- 

 mals on which they 

 feed, from the water 

 drawn in with them 

 (Fig. 69). A few are 

 entirely destitute of 

 teeth, as the ant-eater 

 (Fig. 70). 



217. Though all the 

 Fig. 69. vertebrates possess jaws, 



it must not be inferred that they all chew their food. 

 Many of them swallow their prey whole ; as most birds, 

 tortoises, and whales. Even those which are furnished 

 with teeth do not all of them masticate their food ; some 

 use them merely for seizing and securing their prey, as 

 we find in the lizards, frogs, crocodiles and the great 

 majority of fishes. In such animals, it has been remarked 

 that the teeth are nearly all alike in form and structure, as 



Fisr. 71. 



Fig. 72. 



for instance in the alligator (Fig. 71) ; and in most fishes. 

 A few of the latter, some of the Rays, for example, have 

 a sort of bony pavement (Fig. 72), composed of a peculiar 



