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STRUCTURE AND CLASSIFICATION OF BIRDS 



pigeons. The sternum has both spina externa and interna ; it 

 has two pairs of notches (Goitra), or one pair of notches and 

 one pair of foramina (Phaps, Carpophaga). 



The furcula is U-shaped without hypocleidium. The 

 coracoids may meet, but they do not overlap. 



The following table gives the variations of the principal 

 variable organs in a number of genera : 



