LIMB GIRDLES 357 



of its half of the girdle and lies against its fellow in the middle 

 line. These two are best called collectively the procoracoid. 

 The junction of the two halves of the girdle is known as its 

 symphysis. Scapula and coracoid are cartilage bones. A pair of 

 slender membrane bones, the clavicles, overlie the precoracoid 

 cartilages. Each sends forward a prolongation inside the acromion 

 process. At the junction of the scapular and coracoid bones is the 

 glenoid cavity, a hollow, Hned by cartilage, on the hinder edge 

 of the girdle, into which fits the head of the humerus or bone of 

 the upper arm. 



To the ends of the epicoracoids, before and behind the girdle, 



Fig. 272. — The shoulder girdle of a frog, seen from below, with the right scapula 

 removed, and the left suprascapula bent ventral wards, so that it appears to 

 lie in the same plane as the scapula. 



acr.. Acromion process ; c./., coracoid fontanelle ; c/., clavicle ; cor., coracoid ; e.c, epicoracoid ; ep., epi- 

 sternum ; g.c, glenoid cavity; h., head of humerus; om., omosternum ■,p.c., procoracoid ; sc, scapula; 

 sup., suprascapula; x., xiphisternum ; x.c, xiphoid cartilage. 



are attached certain structures which correspond to the breastbone 

 or sternum of other animals. In front is a bone known as the 

 omosternum, bearing at its end a small plate of cartilage, the 

 episternum. Behind is the larger xiphisternum, bearing the broad, 

 flat xiphoid cartilage. 



The pelvic or hip girdle (Fig. 273) lies at the hinder end of 

 the trunk in a position similar to that occupied in front by the 

 shoulder girdle, which it also resembles in consisting of two 

 halves, each composed of several pieces, joined below in a sym- 

 physis. Its shape, how^ever, is very different ; it is connected 

 with the backbone not solely by muscles, but also by joints or 

 articulations with the large transverse processes of the sacral 

 vertebra ; it bears no bone comparable with the clavicle and 



