50 THE SKELETON OF THE FROG 



forms tte shoulder-joint. The pai-t of the arch ahove the joint 

 is the ^capillar portion : and the part below, which is divided 

 into ajiterior and posterior divisions, the coracoid portion, 



a. The scapular portion is divided into two parts. 



i. The suprascapula, the upper portion, is a thin 

 expanded plate of cartilage overlapping the first 

 four vertebrae : it is partly calcified and partly 

 ossified, though very imperfectly. 



ii. The scapula is an oblong bony plate, constricted in 

 the middle, and forming the upper half of the 

 glenoid cavity, or cavity of the shoxilder- joint. 



b. The coracoid portion forms the lower half of the glenoid 



cavity : it is divided into anterior and posterior por- 

 tions, separated by the coracoid foramen. 

 i. The precoracoid is a slender horizontal bar of car- 

 tilage connecting the anterior edge of the scapula 

 with the sternum. 



ii. The clavicle is a slender bone, closely applied to the 

 anterior border of the precoracoid ; its outer or 

 scapular end is bent forwards almost at a right 

 angle. 



iii. The coracoid is a stout bone, wider at its inner 

 than its outer end : it connects the posterior 

 edge of the scapula with the sternum. 



iv. The epicoracoids are a pair of narrow strips of 

 cartilage closely applied to each other, and lying 

 between the ventral ends of the precoracoids and 

 coracoids. 



c. The sternum lies in the mid-ventral line : it consists 



originally of two lateral halves, which fuse com- 

 pletely in front and behind, but remain distinct 

 in the median portion. It presents from before 

 backwards the following parts : 



i. The presternum. 



a. The epistemum is a flat circular plate of car- 

 tilage. 

 /3. The omosternum is a slender bony rod pro- 

 jecting forwards in front of the clavicles. 



