108 COMPARATIVE MORPHOLOGY OF VERTEBRATES. 
lost in chameleons and crocodiles, and if present in the chelonians, it is 
represented by the epiplastron (p. 41), an element of the carapace. 
The girdles are greatly reduced in the limbless lizards and have van- 
ished in the ophidians. 
In the BIRDS (fig. 53) the scapula is a sword-shaped bar overlying 
the ribs, while the coracoid extends from its junction with the scapula 
at the glenoid fossa to the anterior end of the sternum. ‘The clavicles 
of the two sides are united at their medial or ventral ends to form the 
well-known furcula (wishbone) which may articulate with the sternum 
between the two coracoids, or, with diminishing powers of flight, may 
end freely below. 
FIG. 112. FIG. 113 
Fic. 112.—Sternum and pectoral girdle of Amblyrhynchus, after Steindacher. c, 
coracoid; cl, clavicle; e, epicoracoid; es, episternum; , humerus; m, mesocoracoid; ms, 
mesoscapula; ~, procoracoid; sc, scapula; s, sternum. 
Fic. 113.—Shoulder girdle of Ornithorhynchus. cl, clavicle; co, coracoid; e, epister- 
num; g, glenoid fossa; pc, procoracoid; s, scapula; st, sternum. r 0 
MAMMALS.—The shoulder girdle of the monotremes is strikingly 
like that of lizards, the coracoids acting as a brace between sternum and 
glenoid fossa, while the resemblance is strengthened by the presence of 
the episternum. This same large development of the coracoids occurs 
in the young of some marsupials, but in the adults, as in the rest of the 
mammals, the coracoid is greatly reduced, persisting only as a small 
projection, the coracoid process, anchylosed to the ventral end of the 
