370 STEEXA OF RUNNING BIRDS. 



at the middle, divided posteriorly into three processes, 

 by means of two deep and wide notches, which are 

 filled by cartilaginous membrane. The middle pro- 

 cess is rather longer than the solid portion of the 

 sternum, and terminates in a blunt point. The lateral 

 ones are more than one and a half times as long, and 

 are a little broadened at the points, and the edge of 

 the membrane between them is concave. These 

 lateral processes are flexible, and may be regarded as 

 oblique sternal ribs for supporting the flanks of 

 the bird, rather than as portions of the sternum in 

 supporting the organs of flight. The middle pro- 

 cess is rendered stiff'er by the keel, which, although 

 not high as compared with that of many other 

 birds, is high in proportion to the width of the 

 sternum. This keel is convex on the under side 

 and concave on the front, the angle pointed, and 

 surmounted by a small bony process outside. The 

 lateral processes are inclined forward and upward, 

 and there are six ribs between them and the posterior 

 lateral ones. Coracoids short, but well formed, and 

 moderately well set forgiving firmness to the shoulder 

 joint. The clavicle is along semi-oval, rather slender, 

 but without any process on the under side at the union 

 of the two branches ; but there is a small tubercular 

 process on the upper side. The scapulars are very 

 long, and a little bent downwards, and thin. 



This sternal apparatus indicates considerable power 

 of flight, though, from its narrowness, the stroke of 

 the wing must be quick and rather feeble. The 

 central posterior process gives a firm support to the 

 middle of the under part of the body ; and the 

 lateral ones, from their great length and flexibility, 

 support the flanks, and at the same time enable the 

 body to accommodate itself to those obstacles among- 



