SKELETON 



phalanges (joints) ; the second the Index, representing man's first 

 finger, with two or three joints ; the tliird a weak digit with only 

 one phalanx, except in Arcliaeoptcryx, where there are four. The 

 Casuarii and Apterijges possess an index only, which in the Sphenisci 

 is fused with the pollex. The basal joint of this is the normal 

 place of attachment of the " l)astard wing" {alula spuria). 

 Archaeopteryx had claws on all its fingers, but in recent Birds 

 they occur on the first two only, being functionless in the adult. 

 Wing-spurs arise from the carpal and metacarpal bones. 



6. The Pelvic Arch consists of the Ilium, Ischium, and Os 

 pubis, these three paired bones meeting from each side at the cup 

 {acetaJjulum) that receives the head of the femur, and coalescing 

 early in life ; while the incisura ischiadica or notch between the 



Fig. 4. — Pelvis of Aptcryx avsfrnUs. Lateral view. «, Acetabiiliuu ; il, ilium : is, iscMuixi ; 

 p, pectineal process of pubis ; .jij\ pubis. (From Wiederslieim, after Marsh.) 



ischium and the ilium becomes an inclosed space (Joramen) in 

 all Birds except the llatitne and Crypturi. 



7. The Posterior Liml)S, or Legs, are composed of the Pemur 

 or thigh, the Tibia and Pibula, making the shank or " drum- 

 stick," and the bonea of the Poot. The thigh, however, being 

 hidden by the plumage, the shank of a Bird might easily be 

 taken for the thigh, and the metatarsus (the cannon-bone of some) 

 for the shank. The tibia and fil)ula commonly unite to som(> 

 extent, and the former, as it now exists in adult Birds, is strictly 

 a " tibio-tarsus," since with it is fused the proximal portion of the 

 originally existing tarsal elements. Similarly the distal tarsal 



