254 



THE SHOULDER GIRDLE. 



[CHAP. 



Myopotamus). There is often a long metacromion, as in the 

 Hare ; but in others, as the Beaver, there is no such process. 

 The coracoid is always a small blunt hook. 



In a few forms the clavicle is altogether absent, in some it 

 is well developed, and various intermediate stages between 

 these two extremes are met with. In some species, as the 

 Guinea Pig and Rabbit, although no trace of this bone is 

 found at birth, it becomes developed at a later period. In 

 both of these it is very short, and is suspended by long 



rnss 



FIG. 79. Shoulder girdle, with upper end of sternum (inner surface), of a young 

 Rabbit (Lepus cuniculus), after Parker, f. ps presternum. ; sr 1 first sternal rib; 

 osl onnsternal cartilage ; pc precoracoid cartilage ; c/ossified clavicle ; mss carti- 

 laginous mesoscapular segment ; c coracoid ; a acromion ; ma metacromion : of 

 anterior fossa : pf posterior fossa. 



ligaments between the scapula and the sternum. (See Fig. 

 79.) In many species, as in the Porcupines, in which the 

 clavicular arch is more complete, the true clavicle is con- 

 nected with the presternum by a long cartilaginous omo- 

 sternum. In others, as the Beaver, this is replaced by a 

 ligamentous band. Rudiments of the sternal end of the 

 coracoid are often present, sometimes cartilaginous, some- 

 times ossified. 



