74 PEOF. W. K. PAEKER ON THE 



respect from all the others except Turnix, in Avhich the distal is nearly one third longer 

 than the middle segment. The humerus of Opisthocomus is almost as well developed 

 as in a Pigeon ; the thick uncinate snag below the head and in front of the large 

 pneumatic foramen is very large, and there is a strong crest for the pectoralis major ^. 



The radius, ulna, and manus are all strong, normally gallinaceous, and indeed very 

 similar to those of Crax glohicera ; the quill-marks on the ulna are less than in Corythaix, 

 but larger than in Crax. The two proximal carpals are now normally ornithic ; all signs 

 of their division are lost (PL X. figs. 8, 9, i.r., cm.). The distal carpals are completely 

 fused with each other and with the three metacarpals (figs. 8, 9, d.c.^, d.c?, d.c?; mc.^, 

 mc.^, mc.^). The trochanter on the short first metacarpal is low down, but strong ; the 

 first distal carpal (fig. 9, d.c}) is a rounded knob of bone looking obliquely downwards 

 and forwards toward the first metacarpal. The proximal and distal intercalary parts 

 behind the index {mc.^', dg.^') are completely fused with that member. There is a 

 distinct semi-oval ungual phalanx to both the pollex and index {dg}, dg?), and in spite 

 of growth and ossification the distal joint of the third digit {dg.^) is still visible, and 

 also the still more instructive remnant, the aborted phalanx of the fourth finger {dg.'^). 

 Mr. Perrin, in his figures of the wing, shows the unguis both on the index and pollex 

 {ihid. pi. Ixiv. figs. 1,2). 



VII. The Hip-girdle of Opisthocomus cristatus. 

 In the 1st stage (Pis. VII. & IX. figs. 4 & 5) the moieties of the hip-girdle are 

 scarcely more than half ossified ; they have already acquired their permanent form and 

 position, and are passing from the Ornithoscelidan, through the Struthious, to the 

 normal Carinate condition. Thus the axes of the pre-ilium and pubis are nearly 

 coincident {pr.i., ph.), and the ischium is still separate from the post-ilium {pt.i.). The 

 post-ilium is only three fourths the length of the pre-ilium ; this has only a short tract 

 of cartilage in front ; the other part is largely unossified at present. The two moieties 

 are now a great width apart — one third more than their own breadth ; this is due to 

 the large relative size of the sacral chain of vertebrae. The pre-ilia narrow in forwards 

 sinuously ; the post-ilia at the hinder part of the acetabulum form the projecting facet, 

 right and left, for the articular surface of the trochanter major. They then narrow in 

 suddenly, and again widen out to form the projecting eaves of the pelvis; they then 

 become narrow and die out, and the end of the post-ilium has a sub-uncinate form ; it is 

 slightly curved inwards. Under the projecting eave the post-ilium grows downwards 

 in its last two-thirds to meet the ischium ; its fore third is deficient, and thus forms 

 the sacro-ischiatic space (s.i.f.). The three elements of the hip fail to join completely 

 at the acetabulum, which is always, in birds, open within. The ischium (isc.) reaches 



' That iQusole is really very massive (see Mr. Perrin's valuable paper. Trans. Zool. Soc. vol. ix. pi. Isiii. 

 fig. 3). 



