FROG : EXTERNAL FEATURES AND BODY- WALL 37 



glenoid cavity, a hollow, lined 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, are attached certain structures which are analogous 

 to the breastbone or sternum of other animals. In iront is a 

 bone known as the omosternum, bearing at its end a small 

 plate of cartilage, the episternum. Behind is the larger 

 xiphisternal, bearing the broad, fiat xiphoid cartilage. 



sup. 



cl. 



Fig. 17. — The shoulder girdle of a frog, seen from below, with 

 the right scapula removed. 



acr., Acromion process ; c.f. t coracoid fontanelle ; cl., clavicle ; cor., cora- 

 coid ; e.c, epicoracoid ; ep., episternum ; g.c, glenoid cavity ; h., head 

 of humerus; om., omosternum; p.c. , precoracoid ; sc, scapula; sup., 

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



The hip girdle or pelvic arch 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 symphysis. Its shape, however, is very different; 

 it is connected with the backbone not solely by muscles, 

 but also by joints or articulations with the large trans- 

 verse processes of the sacral vertebra; it bears no bone 

 comparable with the clavicle, and there are in connection with 

 it no unpaired structures such as the sternum. The greater 

 part of each half consists of a long slender bone, the hip- 



