36 



THE ANATOMY OF VEETEBRATED ANIMALS. 



coracoids are large, and articulate -with the antero-extemal 

 margins of the piimitively cai-tilaginoixs sternum, or breast- 

 bone. But, in most mammals, they do not reach the ster- 

 num, and, becoming ankylosed with the scapula, they 

 appear, in adult life, as mere processes of that bone. 



Numerous Vertebrates possess a clavicula, or collar-bone, 

 which is connected with the pre-axial margin of the sccqnda 

 and coracoid, biit takes no part in the formation of the 



Fig. 13. 



ficr- 



Fig. 13.— Ventral view of the sternum and pectoral archei of Iguana 

 tuherculata. The letters as in Fig. 12. 



glenoid cavity, and is usually, if not always, a membrane 

 bone. In many Vertebrata, the inner ends of the clavicles 

 are connected with, and supported by, a median membrane 

 bone which is closely connected with the ventral face of 

 the sternum. This is the interclavicula, frequently called 

 episternum. 



