CHAP. II] 



THE MAMMALIA 



Episfernum -Sternum 



21 



--Clavicle 



Scapula 



Procoracoid 

 -""&coracoid 



Humerus 



Fig. 8. Shoulder girdle of a Eeptile (Iguana) ; to shew the elements of the 

 girdle in a comparatively undifferentiated condition. 



Clavicle ^„5capula 



J! _„ -Procoracoid 

 Xoracoid 



Humerus 



Fig. 9. Shoulder girdle of a Prototherian Mammal (Echidna) ; to be compared 

 with Fig. 8. Several of the primitive constituent elements of the girdle are still 

 distinct. 



