SKELETON. 



663 



The sternum bears a conspicuous keel, is produced 

 laterally and posteriorly into two xiphoid processes, and 



Isch. 



... 



FIG. 366. Side view of pelvis of cassowary. 

 II., Ilium ; fsch., ischium ; Pb., pubis ; Ac., acetabulum. 



bears articular surfaces for the cora- 

 coids anteriorly, for the sternal ribs 

 laterally. 



The skeleton of the wing includes 

 the stout humerus, the separate radius 

 and ulna (the latter the larger), two 

 free carpals, a carpo-metacarpus of 

 three metacarpals fused to one another 

 and to some carpal elements, and three 

 digits the thumb with one joint, the 

 first finger with two joints, the second * 

 with one. In adaptation to flight, the 

 wing of a bird has much less flexibility 

 of parts than the arm of a Mammal. 

 The radius and ulna do not move upon 

 each other. 



The pelvic girdle consists of dorsal 

 ilia fused to the complex sacral region, 

 of ischia sloping backwards, and of 

 pubes running parallel to the ischia. 

 The incomplete ossification of the 

 acetabulum and the absence of ventral 

 symphyses are noteworthy. 



The hind-limb consists of a short 

 stout femur, a tibia to which the 

 proximal tarsals (astragalus and os J 

 calcis) are fused (forming a tibio-tar- 

 sus), an incomplete fibula joined to 



FIG. 367. Bones of 

 hind-limb of eagle. 



.> Femur ; /./. ,tibio-tarsus ; 



Jib., fibula; a., ankle- 

 joint ; ;//./., tarso-meta- 

 tarsus ; ;//./., first nieta- 

 tarsal (free). 



