CHARACTERS OF AVES. 463 



of the three toes which are directed forwards, consists of three 

 phalanges ; the next ha.s four phalanges ; and the outermost or 

 "little" toe is made up of /w« phalanges (fig. 182, A). This 



Fig. 182. — A, Hind-limb of the Loon {Colymhiis glacidlis) — after Owen :"« Innominate 

 bone ; /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'; pfi Phalangesof the toes ; E, 

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



increase in an arithmetical ratio of the phalanges of the toes, 

 in proceeding from the inner to the outer side of the foot, ob- 

 tains 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 backwards, so that there 

 are two toes in front and two behind. 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 



