404 SKELETON OF THE FOWL. 



projecting from the anterior end and ventral 

 surface of the body. 



ii. The carina, or keel, is a very prominent triangular 

 crest projecting downwards from the ventral 

 surface of the sternum, and slightly thickened 

 along its anterior border, which is concave. 



iv. The metostea are a pair of large processes, pro- 

 jecting backwards from the sides of the 

 anterior end of the body ot the sternum. 

 Each divides, close to its origin, into two 

 large flattened processes, the external an 

 middle xiphoid processes, which are ex- 

 panded at their hinder ends. 



V. The costal surfaces are the lateral borders of 

 the body, in front of the metostea ; they are 

 notched for the sternal ends of the ribs. 



vi. The costal processes project forwards and out- 

 wards, in front of the costal surfaces. 



vii. The coracoid grooves are a pair of deep trans- 

 verse grooves on the anterior end of the. body 

 of the sternum, continuous with each other, 

 across the median plane, through a hole in 

 the base of the manubrium. With them the 

 ventral ends of the coracoid bones articulate. 



C. The SkuU. 



The chief characteristics of the bird's skull are : — (1) its 

 great lightness ; (2) the very extensive fusion of the bones 

 of the cranium with one another, most of the cranial sutures 

 being closed, and the outlines of the bones obliterated, by the 

 end of the first year ; (8) the large size of the orbits, which 

 are separated from each other by a thin vertical interorbital 

 septum ; (4) the prolongation of the face forwards into a long 

 conical toothless beak. 



The skull consists of the same essential parts as that of 

 the rabbit, from which, however, it differs in the following 

 important points : (1) there is only a single occipital condyle, 



