SKELETON. IOy 



large round element is called the coracoid. In the recent amphibians 

 we are on firmer ground. The halves of the girdle develop separately, 

 and the cleithrum is lacking. In urodeles the coracoid region has two 

 processes diverging from the glenoid fossa, an anteriorly directed pro- 

 coracoid and a coracoid proper, directed toward its fellow of the 

 opposite side, the two meeting the sternum behind and overlapping in 

 front. Ossification sets in in the neighborhood of the glenoid fossa, 

 the resulting bone being called the scapula, although it invades the 

 coracoid region, the cartilage dorsal to it being the suprascapula. 



In the toads and allied anura (arcifera) the halves of the girdle 

 overlap as in the urodeles, but the procoracoids extend toward the 

 middle line, each being joined to its coracoid by longitudinal cartilage 

 plate, the epicoracoid, leaving a gap between them. With the ap- 

 pearance of bone, scapula and coracoid ossify, while a clavicle of mem- 



FIG. in. Arciferous girdle of Ceratophrys ornatus. cl, clavicle; co, coracoid; e, epicora- 

 coid; h, head of humerus; s, scapula; 55, suprascapula; cartilage dotted. 



branous origin overlies the procoracoid cartilage. In the frogs (firmi- 

 sternia) the relations are much the same, except that the epicoracoids, 

 instead of overlapping, abut against each other, and the clavicles nearly 

 or quite replace the procoracoid, while sternum and omosternum join 

 the girdle in front and behind. Girdles are lacking in the gymnophiones. 

 REPTILES. With the development of a considerable neck in the 

 reptiles the pectoral girdle is removed farther from the head; it shows 

 considerable differences in the various groups. In the fossil rhyn- 

 chocephals it is much as in the stegocephals, except that the scapula 

 is large. In the turtles it occupies a peculiar position, being inside 

 the carapace, i.e., internal to the ribs; but this is explained by the de- 

 velopment; the girdle arises in front of the ribs and later sinks to the 

 definitive position. Scapula, procoracoid and coracoid are well 

 developed, the medial ends of the latter two being connected by a cartil- 

 aginous epicoracoid. Elsewhere in the reptiles the procoracoid tends 

 to reduction, the clavicle taking its place, though it is retained in the 

 lizards in a reduced condition (fig. 112). The clavicle in turn is 



