2 5 6 



THE SCIENCE OF LIFE. 



The Gavials, or Crocodiles of the Ganges, have the jaws 

 produced to an enormous length. 



5. CLASS IV. AVES, or Birds, are warm-blooded Ver- 

 tebrates, clothed with feathers. 



The bones of Birds are very compact and ivory-like, 

 yet lighter than those of Reptiles or Mammals. Many 





FIG. 153. i. Crocodile, {Crocodilus vulgaris^ 2. Alligator, {Alligator lucius.) 

 3. Lizards. 



parts of the skeleton are fused, or anchylosed together. 

 The lumbar vertebrae are wanting, but the neck con- 

 tains from nine to twenty-four vertebrae, rendering it 

 quite flexible. The sternum is strong, and in birds of 



