APPENDIX 205 
Class 2. Amphibia. Amphibians. Vertebrates with gills during a 
part or all of their life, and usually with lungs; scales mostly absent. 
Ex. Rana. 
Class 3. Reptilia. Reptiles. Vertebrates with body covered with 
horny scales or plates and without gills. Ex. Coluber. . 
Class 4. Aves. Birds. Feathered vertebrates whose anterior ap- 
pendages are wings. Ex. Gallus. 
Class 5. Mammalia. Mammals. Hair-covered vertebrates which 
suckle their young. Ex. Felis. 
