SEC. Ill EXTERIOR PARTS OF BIRDS 175 



tailed" gracMe has been so named on this account. One of the 

 most beautiful and wonderful of all the shapes of the tail is illus- 

 trated by the male of the lyre-bird {MIenura superba. Fig. 32), in 

 which the feathers are anomalous both in shape and in texture, and 

 the resulting form of the whole is unique. It should be remembered 

 that, to determine the shape, the tail should be nearly closed ; for 

 spreading will make a square tail round, an emarginate one square, 

 etc. I give a diagram of the principal forms (Fig. 33). 



IV. THE FEET. 



The Hind Limbs, in all birds, are organised for progression — all 

 can walk, run, or hop on land, though the power to do so is very 

 slight in some of the lower swimming birds, as loons and grebes, 

 and certain of the lower perching birds, as hummers, swifts, goat- 

 suckers, and kingfishers. They are specially fitted for perching on 

 trees, bushes, and other supports requiring to be grasped, in the 

 great majority of birds, as throughout the Passeres, Picarice, Accvpitres, 

 Golumhce, and, in fact, many water-birds ; there being few forms, 

 mainly found among three-toed birds, or those in which the hind 

 toe is short, weak, and elevated, in which the extremity of the limb 

 has not decided grasping power. The limb becomes a paddle for 

 swimming either on or in the water in many cases. In not a few, 

 as parrots and birds of prey, the foot is serviceable as a hand. 

 Those kinds of birds which live in trees and bushes habitually 

 progress, even when on level ground, in a series of hops, or rather 

 leaps, both feet being moved together : in all the lower birds, how- 

 ever, the feet move one after the other, as in ordinary walking or 

 running. The modifications of the hind limb are more numerous, 

 more diverse, and more important in their bearing on classification, 

 than those of either bill, wing, or tail ; their study is consequently 

 a matter of special interest. 



Their Bony Framework (Fig. 34). — Beginning at the hip-joint, 

 and ending at the extremities of the several toes, the skeleton of 

 the hind limb consists in the vast majority of adult birds of twenty 

 bones. This is the typical and nearly the average number ; birds 

 scarcely ever have more, and the principal lessenings of the number 

 result from the absence of one or two toes, or a slight reduction in 

 the number of the joints of some toes, or absence of the knee-cap. 

 Of the normal twenty, fourteen are bones of the toes ; one is an in- 

 complete bone connecting the hind toe with the foot ; one is the 

 knee-cap, and four are the principal bones of the thigh (1), leg (2), 

 and foot (1). The first or uppermost is the thigh-bone or femur 

 (Lat. femur ; adjective, femoral), fm, from hip to knee, ^ to -B in the 

 figure. It is a rather short, quite stout, cylindrical bone, enlarged 



