500 



THE VERTEBRATE SKELETON. 



broad at the distal end and having well marked deltoid and 

 supinator ridges, which are specially large in Notoryctes. An 



FIG. 105. ANTERIOB SUKFACE OF THE BIGHT HUMEKUS OF A WOMBAT 



(Phascolomys latifrons). (After OWEN.) 



head. 6. 



greater tuberosity. 7. 



lesser tuberosity. 8. 



deltoid ridge. 9. 



ent-epicondylar (supracondy- 10. 

 lar) foramen. 



supinator ridge, 

 external condyle. 

 internal condyle. 

 articular surface for radius, 

 articular surface for ulna. 



ent-epicondylar or supracondylar foramen (fig. 105, 5) is almost 

 always present except in Notoryctes. The radius and ulna are 

 always distinct and well developed, and a certain amount of 

 rotation can take place between them. The ulna of Notoryctes 

 has an enormous hooked olecranon which causes the bone to 

 be nearly twice as long as the radius. 



EDENTATA. The Sloths have long slender arm bones ; the 

 humerus is nearly smooth and has a very large ent-epicondylar 

 foramen in Choloepus, but not in Bradypus. The radius 



