204 ZOOTOMY. 



rudimentary first metacarpal is the single phalanx of the first 

 digit or pollex : the second digit has two phalanges, the 

 proximal one (ph. 2] being flattened and very thin on its 

 post-axial side, the distal one (p/i.2 J ) pointed and concave 

 dorsally : the third metacarpal bears a single pointed 

 phalanx (ph. 3). 



101. In the young bird the metacarpals are distinct bones 

 with cartilaginous epiphyses. 



XIV. Make out the characters of the pelvis or hip 

 girdle as follows : 



102. It consists of two paired bones, the ossa inno- 

 minata (Fig. 50), more or less extensively ankylosed to 



n 



obf is 



fu 



FIG. 50. Columba livia. Left os innominatum of a nestling 

 (fourteen days), viewed from without ( x 2). 



The cartilage is distinguished by dotting. 



ac, acetabuluin : a.tr, anti-trochanter : il, pre-, and z7, post- 

 acetabular portion of ilium : is, ischium : t.s.f, ilio-sciatic foramen : 

 ob.f t obturator fissure : pu, pubis. 



the sacrum in the adult, but easily separable in the young 

 bird. 



103. The acetabulum (Fig. 48, ac),& rounded articular 

 cavity on the outer surface of each os innominatum, per- 

 forated by an aperture, and serving for the articulation of the 

 leg : its postero-dorsal region is prolonged into a distinct 

 facet, the anti-trochanter (a.tr). 



