SKELETON 



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

 finger, with two or three joints ; tlie third a weak digit with only 

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

 C'i(sii((rii and Apfcri/ges possess an index only, which in the Sphenisci 

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

 place of attachment of the "hastard wing" (alula spuria). 

 Archaeopte'njx 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 

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

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



Fig. 4. — Pelvis of Apteryx australis. Lateral view, a, Acetabulum ; il, ilium ; is, isoHum : 

 jj, pectineal process of pubis ; i)\ pubis. (From Wiedersheim, after Marsh.) 



ischium and the ilium becomes an inclosed space {foramen) in 

 all Birds except the Eatitae and Cnjjifuri. 



7. The Posterior Limbs, or Legs, are composed of the Femur 

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

 stick," and the bones of the Foot. 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 fibula commonly unite to some 

 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 



