582 



MANUAL OF ZOOLOGY. 



by anchylosis. The femur or thigh-bone (fig. 325, A, f) is 

 generally very short, comparatively speaking. The chief bone 

 of the leg is the tibia (/), to which a thin and tapering fibula (r) 



Fig. 325. A, Hind-limb of the Loon (Colymbus glacialis) after Owen : z" Innominate 

 bone ; f Thigh-bone or femur ; t Tibia, with the proximal portion of the tarsus an- 

 chylosed to its lower end ; r Fibula ; m Tarso-metatarsus, consisting of the distal 

 portion of the tarsus anchylosed with the metatarsus ; p p Phalanges of the toes. B, 

 Tail of the Golden Eagle; s Ploughshare-bone, carrying the great tail-feathers. 



is anchylosed. The upper end of the fibula, however, articu- 

 lates with the external condyle of the femur. The ankle-joint 

 is placed, as in Reptiles, between the proximal and distal 

 portions of the tarsus. The proximal portion of the tarsus, 

 consisting of two bones, representing the astragalus and cal- 

 caneum or the former only, is undistinguishably amalgamated 

 with the lower end of the tibia. The distal portion of the 

 tarsus is anchylosed with the second, third, and fourth meta- 

 tarsals to constitute the most characteristic bone in the leg of 

 the Bird the " tarso-metatarsus " (m). In most of the long- 

 legged birds, such as the Waders, the disproportionate length 

 of the leg is given by an extraordinary elongation of the tarso- 

 metatarsus. 



