250 BIRDS. ' 



portion of the tarsus, consisting of two bones representing 

 the astragalus and calcaneum or the former only, is unclis- 

 tinguishably amalgamated with the lower end of the tibia. 

 The distal portion of the tarsus is anchylosed with the second, 

 third, and fourth metatarsals to constitute the most charac- 

 teristic 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 extra- 

 ordinary elongation of the tarso-metatarsus. 



The tarso-metatarsus is followed inferiorly by the digits 

 of the foot. In most birds the foot consists of three toes 

 directed forwards and one backwards — four toes in all. In 

 no wild bird are there tnorc than four toes, but often there 

 are only three, and in the Ostrich the number is reduced to 

 two. In all birds which have three anterior and one posterior 

 toe, it is the posterior thumb or hallux (that is to say, the 

 innermost digit of the hind-limb) which is directed back- 

 wards ; and it invariably consists of two phalanges only, its 

 metatarsal being incomplete and united, as a rule, to the tarso- 

 metatarsus by ligament only. The most internal of the three 

 anterior toes (the " index ") consists of three phalanges ; the 

 next (" middle ") has four phalanges ; and the outermost toe 

 ("annularis") is made up of five phalanges (fig. 584, a). 

 This increase in an arithmetical ratio of the phalanges of the 

 toes, in proceeding from the inner to the outer side of the 

 foot, obtains in almost all birds, and enables us readily to 

 detect which digit is suppressed, when the normal four are 

 not all present. Variations of different kinds exist, however, 

 in the number and disposition of the toes. In many birds 

 — such as the Parrots — the outermost toe is turned back- 

 wards, so that there are two toes in front and two behind ; 

 whilst in the Trogons the inner toe is turned back with the 

 hallux, and the outermost toe is turned forwards. In others, 

 again, the outer toe is normally directed forwards, but can be 

 turned backwards at the will of the animal. In the Swifts, 

 on the other hand, all four toes are present, but they are all 

 turned forwards. In many cases — especially amongst the 

 Natatorial birds — the hallux is wholly wanting, or is rudi- 

 mentary. In the Emeu, Cassowary, Bustards, and other 



