310 GENERAL ZOOLOGY 



B. Vertebrates (Continued) 



Class 2. Amphibia: breathe by gills or lungs, skin, 

 moist, usually two pairs of legs. Ex. Rana 

 clamitans. 



Class 3. Reptilia: breathe by lungs, body covered 

 with dry scales, heart with three cham- 

 bers. Ex. Sceloporus undulatus. 



Class 4. Aves: breathe by lungs, body covered with 

 feathers, heart with four chambers. Ex. 

 Columba livia. 



Class 5. Mammalia: breathe by lungs, body covered 

 with hair, heart with four chambers, suckle 

 young. Ex. Sciurus carolinensis. 



