AVES 265 



is keeled in our birds, while the keel is lacking in the ostrich. 

 The keel or carina is a basis of classification. Birds with the 

 keel poorly or not at all developed are called Ratl'tce, or raft-like 

 birds, while the keeled birds are called Carina'tce, which group 

 contains our native American birds. 



The shoulder-girdle is a peculiar device of flying creatures. 

 It consists of the scapula, coracoid process, and the V-shaped 



Fig. 216. — Skeleton of a sparrow: q, Quadrate bone, peculiar to reptiles 

 and birds and some amphibia; b, breast-bone; m, merry-thought or collar- 

 bone; c, coracoid bone, over which the tendon works to pull up the wing; 

 p, plowshare-bone, on which the tail grows. Wing-bones: a. Upper-arm; 

 e, elbow; fa, fore-arm; w, wrist; t, thumb; ha, hand. Leg-bones: th, Thigh- 

 bone; k, knee; I, lower part of leg; h, heel; /, foot. (From Holder, Amer- 

 ican Book Co., Publishers.) 



clavicle, or "wish-bone." The pelvic girdle consists of three 

 paired bones, ilium, ischium, and os pubis, which unite at the 

 cup or acetabulum, which holds the head of the femur. 



A careful study of the skeleton of a bird shows its marvelous 

 adaptation to its uses. It must be strong to support the great 

 muscles of flight and to protect the viscera, while it must be light 

 and flexible for the purpose of aerial locomotion. 



