30 GENERAL HISTORY OF BIRDS. 



process for the clavicular end of the fourchette or furcula. When in situ 

 the blade of the scapula lies along the dorsum over the tops of the ribs and 

 nearly parallel with the vertebral column. 



A coracoid has a shaft, a head, which is the tuberous upper end, and an 

 expanded lower extremity. This latter fits in the coracoidal groove of the 

 sternum, already referred to above. When thus articulated it may meet the 

 fellow of the opposite side, or it may even decussate with it, or cross it, while 

 in Rhea the bones are widely apart in this place. Above, the coracoid contri- 

 butes to the glenoid cavity about two-thirds of its articular surface. It has a 

 clavicular process for the end of the furcula, and it also articulates with the 

 scapula. In rare instances, anchylosis takes place between the scapula, 

 coracoid, and end of the furcula, where they mutually articulate. 



In all flying birds, whether existing or extinct, the pectoral limb, or skele- 

 ton of the wing, is well -developed, while in the flightless forms, such as the 

 Kiwi, the Ostriches and Hesjjerornis, it is more or less aborted. 



In any bird possessed of full volant power, the skeleton of the forelimb 

 is divided into brachium, or arm, consisting of the himierus; antibrachium, or 

 forearm, containing the radius axiA ulna, and the pinion, which is the manus or 

 hand, where we find tv:o carpal hones, the metacarpus, and the bones of the 

 threi' digits, — poUex, index and medius. 



As a rule, the humerus in all ordinary birds has both its proximal and 

 distal extremities expanded; the first to articulate with the shoulder-girdle, 

 and the latter to support the two trochlese for articulation with the radius and 

 ulna of the forearm. On its ventral aspect is developed a preaxial, or pectoral 

 ridge for the insertion of the muscle of that name. When pneumatic, the 

 foramina occur in the pneumatic fossa at the proximal extremity. Usually 

 the shaft is cylindrical, smooth, and presents a sigmoid curve. It may be, 

 however, more or less flattened and solid, as in the Penguins. Radius and 

 ulna are both, long and slender, the former generally being not more than 

 half the calibre of the last, and either may be straight for their continuity or 

 gently curved or bowed. Distally, they articulate with the two bones of the 

 carpal joint, — the radiale and vlnare. The ulna may show a row of bony 

 papillae down its shaft for the insertion of the quill-butts of the secondary 

 feathers of the wing, and its proximal end, a process, the olecranon of the ulna. 

 Near it is received the "head of the radius," and both articulate with the 

 humerus. In the skeleton of manus in the Apteryx and in the Casuariidw there is 

 but a single complete digit, clawed at its extremity (index), while in all other 

 birds, so far as known to the present writer, including the various forms of 

 existing Ostriches, there are the three digits named above, the index having 

 two joints, to which a claw may be added (swan). The much reduced medius 

 digit never bears a claw in the adult. In the compounded metacarpal bone, 



