Aves. 



2 45 



General Characteristics of Birds. The possession of 

 feathers is sufficient to distinguish birds from all other 

 animals. The consolidation of the thoracic vertebrae and 

 the pelvis is peculiar. The bones of the cranium are 

 united in one, the sutures disappearing early. The ribs 

 are provided with flat braces extending to adjoining ribs. 

 The breastbone is large, and usually has a well-developed 

 keel. The two collar bones (clavicles) unite to form a wish- 

 bone. Air sacs are connected with the lungs. The tem- 

 perature of the blood is high. The red corpuscles are 

 elliptical and have nuclei. The brain is relatively large, 

 the eye especially being large in proportion to the size 

 of the head. The organ of the voice is at the lower end of 

 the windpipe, instead of at the upper. 



CLASSIFICATION OF BIRDS. 



f Division Ratitse 



Class Aves 



Division Carinatae 





