494 



THE VERTEBRATE SKELETON. 



there is also a large T-shaped interdavicle (fig. 102, 4), 

 which is expanded behind and rests on the presternum. The 

 clavicles rest on and are firmly united to the anterior border 

 of the interclavicle. This shoulder girdle differs greatly from 

 that of any other mammals, and recalls that of some Lacertilia. 

 In MARSUPIALS, as in all mammals except the Monotremes, 

 the shoulder girdle is much reduced ; there are no epicoracoids 



A. B 



FIG. 102. A, SIDE VIEW, B, DORSAL VIEW OF THE SHOULDER GIRDLE AND 



PART OF THE STERNUM OF THE SPINY ANTEATER (Echidna 



x 1. (After PARKER.) 



1. scapula. 6. epicoracoid. 



2. suprascapula. 7. 



3. clavicle. 8. 



4. interclavicle. 9. 



5. coracoid. 10. 



glenoid cavity, 

 presternum. 

 second sternal rib. 

 second vertebral rib. 



and interclavicle, and the coracoid forms simply a small process 

 on the scapula, ossifying from a centre separate from that 

 giving rise to the rest of the bone. The scapula has a long 

 acromion, and a clavicle is always present except in Perameles. 

 Unossified remains of the precoracoids are found at either end 

 of the clavicle. The scapula of Notoryctes has a very high 



