470 MANUAL OF ZOOLOGY sect. 



ends ; the proximal end is produced pre-axially, into an 

 outstanding step-like process. 



The study of its development shows that this bone is 

 formed by the union of the distal carpals with three meta- 

 carpals (Fig. 282), the second and third of which are the 

 two rod-like portions of the bone, the first, the step-like 

 projection. Articulating with the first metacarpal is a single 

 pointed phalanx {ph.i); the second metacarpal bears two 

 phalanges, the proximal one ( ph. 2') produced postaxially 

 into a flange, the distal one {ph. 2") pointed ; the third 

 metacarpal bears a single pointed phalanx {ph. j) . 



Fig. 283. — Columba livia. Left innominate of a nestling. The cartilage is dotted. 

 ac, acetabulum; a tr. anti-trochanter; //, pre-acetabular; and :'/', post-acetab- 

 ular portion of ilium: is. ischium; i s. /, ischiatic foramen; ob. f, obturator 

 notch; pu t pubis. (From Parker's Zootomy.) 



The pelvic girdle (Fig- 283). The ilium (//) is an 

 immense bone, attached by fibrous union with the whole 

 of the syn-sacrum and becoming ankylosed with it in the 

 adult. As usual it furnishes the dorsal portion of the acetab- 

 ulum. The ventral portion of the acetabulum is furnished 

 in about equal proportions by the pubis and ischium 

 (Fig. 283) : it is not completely closed by bone, but is 

 perforated by an aperture covered by membrane in the 

 recent state. Both pubis and ischium are directed sharply 



