BIRDS. 



249 



pubis. The stability of the pelvic arch, necessary in animals 

 which support the weight of the body on the hind-limbs 

 alone, is amply secured in all ordinary cases by the anchy- 

 losis of the ilia with the sacrum. 



As in the higher Vertebrates, the lower limb (fig. 584, a) 

 consists of a femur, a tibia and fibula, a tarsus, metatarsus, 

 and phalanges ; but some of these parts are considerably 

 obscured by anchylosis. The femur or thigh-bone (fig. 584, 

 A, /) is generally very short, comparatively speaking. The 

 chief bone of the leg is the tibia {t), to which a thin and 



pjc. 584. — A, Hind-limb of the Loon (Colymlus glaciaKs)—a.ftei Owen : i, Innominate bone ; 

 / Thigli-bone or femur ; t. Tibia, with the proximal portion of the tarsus anchylosed to its 

 lower end ; r, Fibula ; m, Tarso-metatarsus, consisting of the distal portion of the tarsus 

 anchjdosed with the metatarsus ; j}, P, Phalanges of the toes, b. Tail of the Golden Eagle : 

 s, Ploughshare-bone, carrjdng the great tail-feathers. 



tapering fibula (r) is anchylosed. The upper end of the 

 fibula, however, articulates with the external condyle of the 

 femur. The ankle-joint is placed, as in Eeptiles, between 

 the proximal and distal portions of the tarsus. The proximal 



