THE SKELETON 15 



area for the attachment of the powerful 

 muscles which move the wing. The cranial 

 medial projection or rostrum is short, and 

 pierced at its root by an opening from 

 which extend two elongated, saddle-shaped 

 depressions into which the end of the coracoid 

 bones are received. 



The plate-like process of bone (the posterior 

 lateral process) which projects from the caudal 

 angles of the sternum soon divides into two 

 parts. The shorter of these (the oblique pro- 

 cess) broadens towards its free end and covers 

 the sternal segments of the last two ribs. 



The lateral borders of the sternum are 

 pitted by four or five depressions into which 

 the sternal segments of the ribs are received. 



The dorsal or inner surface of the bone is 

 pierced by openings by which the air -sacs 

 communicate with the interior. 



The Skull (Figs. 3 and 4) 



The presence of large orbits, separated 

 merely by a thin septum formed by the sphenoid 

 and ethmoid bones, permits of ready dis- 

 tinction between the rounded cranium and 

 the pointed, conical face. The cranial part 



