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 



Fig. 111. — Skeleton of the Limbs and Tail of a Cakixate Bird. (The 

 skeleton of the body is indicated by dotted lines. ) 



Sch, scapula ; R, coracoid ; St, sternum, with its keel (Cr) ; OA, humerus ; Rd, 

 ulna ; III, radius ; HW, carpus ; MH, carpometacarpus ; F, digits ; 08, 

 femur ; T, tibiotarsus ; Fi, fibula ; MF, tarsometatarsus ; Z^, Z, digits > 

 Py, pygostyle. 



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

 a position oi 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 



