146 



GENERAL OBNITHOLOGT. 



scapular arch, corresponding to the ratite and cariuate sternum. (1) In Batitts the axes of the 

 coracoid and scapula are nearly coincident (for the most part in a continuous right Une) 'and 

 anchylosed together; the clavicles are usually wanting, or defective; and the coracoids are in- 

 stepped on ^e sternum far apart. (3) In aU Carmatee, the axes of the coracoid and scapula 

 form an acute or scarcely obtuse angle (fig. 56, sgW) ; normally these bones are not anchylosed; 

 perfect clavicles are present, Snchylosed vrith each other, but free from the other bones ; and the 

 coracoids are instepped close together. Decided exceptions to these conditions, as in Notornis, 

 are anomalous ; though incompletion of the clavicles repeatedly occurs, as noted below. 



The Coracoid (Gr. Kopa^, korax, acrovV; eiSoj, eidos, form: the corresponding bone of 

 the human subject, which is the stunted " coracoid process of the scapula," being likened to a 



crow's beak ; no applicability in the present case ; 

 figs. 56, c, 59, c) is a stout, straight, cylindric bone, 

 expanded at each end, extending forward, outward, 

 and upward from the fore border of the sternum 

 to the shoulder. Its foot is flattened and splayed 

 to fit in the articular groove of fore border of 

 the sternam already described; it often overlaps 

 that of its fellow on the median line ; is narrower 

 and remote from its feUow in Batita. The head 

 of the bone, irregularly expanded, articulates or 

 anchyloses with the end of the scapula, and also 

 usually with the clavicle. It bears externally a 

 smooth demi-facet, which represents the share it 

 takes in forming the glenoid (Gr. yKrivt], glene, a 

 shallow pit; fig. 59, gV) cavity, which is the socket 

 of the humerus. This articular expansion is the 

 glenoid process of the coracoid : the clauicular 

 process is that by which the bone unites with the 

 clavicle. The relation between the heads of the 

 three bones (each uniting with the other two) is 

 such that a pulley-hole is formed, through which 

 plays the tendon of the pectoral muscle which ele- 

 vates the wing. The coracoid is a very constant 

 and characteristic bone of birds. 



Fig. 69. — Eight pectoral arch of a bird, Pedia- 

 cetes phasicmelius, nat. size, outeideview; Dr. B. 

 W. Shufeldt, TJ. S. A. s, scapula; c, coracoid; gl, 

 glenoid, the cavity for head of humerus ; cl, clavicle ; 

 Ac, hypooleidium. In situ, the right end of the fig- 

 ure should tilt up a little ; see fig. 66. 



The Scapula (Lat. scapula, the shoulder- 

 blade; figs. 56, 59, s) merits in birds its name of 

 ''blade-bone," being usually a long, thin, narrow, 

 sabre-like bone, which rests upon the ribs — usu- 

 ally not far from parallel with the spinal column, and near it; but in Batitte otherwise. 

 It seldom gains much width, and is quite thin and flat in most of its length; but it has a 

 thickened head or handle, expanding outwards into a glenoid process which unites with that 

 of the coracoid to complete the glenoid cavity, and dilated inward to form - an acromial (Gr. 

 mepaiuov, ahromion, point of the shoulder) ^ocess for articulation with the clavicle (as it-does in 

 man), when that bone exists. The other end is usually sharp-pointed, but may be obtuse, or 

 even clubbed, as in a woodpecker. The scapula is broadest and most plate-like in the pen- 

 guins, in which birds aU the bones of the flipper-like wing are singularly flattened. In Apteryx 

 it reaches in length over only a couple of ribs ; in most birds, over most of the thorax; and 

 in some its point overreaches the pelvis. 



