LIMBS 



131 



aerial (Bats) or aquatic (Pinnipedia, Cetacea, Sirenia) mode of life ; 

 or, again, it may give rise to a prehensile organ. In the latter case 

 (Primates) the radius and ulna, instead of being firmly connected 

 together, articulate with one another, the former being capable 



ScK 



FIG. 111. SKELETON OF THE LIMBS AND TAIL OF A CARINATE BIRD. (The 

 skeleton of the body is indicated by dotted lines. ) 



Sch, scapula ; 7?, coracoid ; St, sternum, with its keel (Or) ; OA, humerus ; Rd 

 ulna ; 77, radius ; HW, carpus ; MH, carpometacarpus ; F, digits ; OS, 

 temur ; T t tibiotarsus ; Fi, fibula ; MF, tarsometatarsus ; 2 1 , Z, digits ; 

 Py, pygostyle. 



of rotation round the latter : thus the rnanus can be brought into 

 a position of pronation or of supination. 



The tibia is the most important bone of the shank, and the 

 fibula often becomes fused with it to a greater or less extent ; the 

 ulna also may unite with the radius. Except in the Cetacea, 



K 2 



