XII 



PHYLUM CHORDATA 



467 



the proximal one (ph. 2'} produced postaxially into a flange, 

 the distal one (ph. 2") 

 pointed ; the third 

 metacarpal bears a 

 single pointed phal- 

 anx (ph. j). 



The pelvic girdle 

 resembles that of no 

 other existing Verte- 

 brate (Figs. 260 and 

 266). The ilium (it) 

 is an immense bone, 

 attached by fibrous 

 union with the whole 

 of the synsacrum and 

 becoming ankylosed 

 with it in the adult. 

 As usual it furnishes 

 the dorsal portion of 

 the acetabulum. The 

 ventral portion of the 

 acetabulum is furn- 

 ished in about equal 

 proportions by the 

 pubis and ischium 

 (is. ///.); it is not 

 completely closed by 

 bone, but is perfor- 

 ated by an aperture 

 covered by mem- 

 brane in the recent 



state. Both pubis and ischium are directed sharply back- 

 wards from their dorsal or acetabular ends, and lie nearly 



H H 2 



ra.' 



FIG. [264. Columba livia. Skeleton of the left 

 wing, cp.mtcp. carpo-metacarpus ; hu. humerus ; 

 ph. I, phalanx of first digit; ph. 2', ph.z" ', 



of 



phalanges of second digit ; ph. 3, phalan 

 third digit ; pn.for. pneumatic foramen ; ra. 

 radius ; ra. radiale ; Til. ulna ; /'. ulnare. 



