iv.] SKELETON OF UPPER LIMB. 153 



The bones of the superior extremity of man are of medium 

 development as to numbers, for they may be more numerous 

 (though rarely much so), or less numerous, since we may 

 select a series of forms in which the number gradually 

 diminishes to zero. 



FIG. 127. FRONT VIEW OF SCAPULAR, OR SHOULDER, GIRDLE OF THE SKATE 



Raia clavata. (After Parker.) 

 This figure shows how in this animal the shoulder girdle abuts against each side 



of the vertebral column. 



c, coracoid element ; ec, epicoracoid element ; s, scapular element ; ss, supra- 

 scapular; v, vertebral column cut across vertically and transversely, and 

 showing the canal for the spinal marrow in its midst. 



ii. The SCAPULA of man agrees in the essentials of its 

 composition with that of every species of his class except the 

 Monotremes. It agrees, that is, in having the coracoid pro- 

 cess annexed to it as a mere process ending freely, and not, 

 as in the Monotremes and in most lower Vertebrates, where 

 the coracoid is a distinct and largely developed bone, ex- 

 tending down to the sternum. 



FIG. 128. SHOULDER GIRDLE OF A BIRD (DIVER). (After Parker.) 



c, right coracoid (its lower end abuts against the sternum here removed) : 

 Cf, the clavicles (merrythought) ; sc, the right scapula the rounded glenoid 

 surface is indicated in the scapula just where it joins the coracoid. 



Man's scapula, apart from this process, is, as we have seen, 

 flat and triangular a shape which, though common, is by 

 no means universal in the Vertebrata. 



Thus, e.g., in Birds we find the scapula to consist of a long, 

 narrow, more or less sabre-shaped bone, though not quite 

 always so, as it becomes considerably broadened out in the 

 Penguin. 



