312 STRUCTURE AND CLASSIFICATION OF BIRDS 



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

 has two pairs of notches (Goura) , 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 foUowing table gives the variations of the principal 

 variable organs in a number of genera : — 



