THE PECTORAL AKCH IN BIRDS. 



289 



tlie skull (the frontal bones being grooved to receive them), 

 and their free ends are inserted between the ascending and 

 maxillary processes of the right premaxilla. 



Fi" 84.* 



Fig. 84. — The right scapula (Sc), and coracoid (Co.) of a Fowl ; gl, 

 the glenoidal cavity ; /, the right clavicle, or right half of the fur- 

 culum ; hp, the hypocleidium. 



The pectoral arch presents a long, narrow, and recurved 

 scapula (8e. Fig. 84*), without any supracapula; and a 

 coracoid (Co.), fitted by its proximal end into the groove 

 in the anterolateral edge of the sternum. The inner ends 

 of the coracoids occasionally o'serlap, as in Lacertilia ; other- 

 wise, the shoulder girdle is unlike that of any of the 

 Beptilia, except the Pterosauria. The coracoid is usually 

 completely ossified, and presents no fontanelle. There is 

 no distinct epicoracoid. The two bones take nearly equal 

 shares in the formation of the glenoidal cavity, and usually 

 remain iinankylosed and distinct in this region. 



In the BatitK the long axis of that part of the scapula 

 which lies near the glenoid cavity is parallel or coincident 

 with that of the coracoid, and the two bones become com- 

 pletely ankylosed. But, in all the Carinatai, the long axis 

 of the scapula forms an acute, or only slightly obtuse 

 angle (Ocydromus, Didus) with that of the coracoid. A 

 small bone, the scapula accessoria, is developed on the outer 



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