362 STERNUM OF THE ROCK DOVE. 



in front, and the angle, though rounded off, is not so 

 much so as in the other. The central portion hack- 

 wards is much more produced, and it is rendered stiff 

 by the continuation of the keel ; but the angles are 

 cut off, which gives the entire bone a sort of lozenge 

 form ; and the sides are weakened by the two holes 



Rock -dove, half the lineal dimensions. 



and two notches which appear in the figure. The 

 coracoids, though not very strong, are much better 

 set at their junction with the sternum than those of 

 the parrot. They have not that direct bearing toward 

 the centre of the sternum which we find in the more 

 typical wing birds ; but their axes do form an angle 

 with each other as seen in front, and the position of 

 the lines of their union tends also to throw the pres- 

 sure on their heads toward the middle of the sternum. 

 The clavicle, though by no means of the strongest 

 form, is much firmer, in comparison with the quantity 

 of matter that it contains, than the clavicle of the 

 parrot. It is an arch, though an elongated elliptical 



