76 PEOF. W. K. PARKER ON THE 



prepubic spur is very small ; it is somewhat larger in Crax, and still larger in Penelope 

 (Huxley, op. cit. p. 298, figs. 3, 4). In the Alectoropodes it is, as a rule, well deve- 

 loped, and also in Tinamous (Tr. Z. S. vol. v. pi. xli. fig. 3 ; Marsh, op. cit. p. 73, 

 fig. 20). The greatest development of this part in the Carinatse is in certain Coccygo- 

 morphse — for instance, Geococcyx (Marsh, op. cit. p. 73, fig. 19, and Shufeldt, Joum. 

 Anat. Phys. vol. xx. pi. 8. figs. 9 & 11); and I find it in a similar state in that 

 American Cuckoo, Saurothera vieiUoti. This bird agrees with the Rallidae, both 

 extinct and existing, in respect of these post-iliac eaves (see Owen on " Aptornis 

 clefossor," Tr. Z. S., vol. viii. pi. 15, and Shufeldt on '■' Porzana Carolina," Journ. of 

 Comp. Med. & Surg. July 1888, art. 17, p. 89, figs. 4 & 5). The existing Rallidae 

 have the prepubic spur very distinct, although rather smaller than in the high-heeled 

 Fowls. There is a family of birds, however, — the Turnicidse — in which the spur is 

 suppressed, and in which, also, the post-ilium forms an eave over the sacro-ischiatic 

 fenestra, exactly as in Opisthocomus — for instance, IIemi])odius varius (Tr. Z. S. vol. v. 

 pi. 35. figs. 5 & 8). The same structure, also, is to be seen in Turnix rostrata. 

 Another peculiarity of the hip-girdle, in which these two types also agree, is the very 

 generalized condition of the ischium in form and in its relation to the pubis. Long 

 ago (Tr. Z. S. vol. v. p. 172), speaking of the congeners of the Hemipods, I remarked : — 

 " These allies are very numerous ; and it is hard to say which of them should be placed 

 nearest this, one of the most ' mixed ' forms in the whole range of Ornithology." This 

 family, the Turnicidse, is not so near extinction as that one-membered family, the 

 Opisthocomidse. 



I will conclude this account of the pelvis of the Hoatzin by giving, for comparison's 

 sake, the length of the pre-ilia and post-alia in six types: — 



Pre-ilium. Post-ilium. 



Corythaix buffoni 24 millim. 21 millim. 



Opisthocomus cristatus 33 „ 27 „ 



Hemipodius varius 21 „ 17 „ 



Turnix rostrata, juv 10'5 „ 7 „ 



Crax glohicera 72 „ 75 „ 



Chauna cliavaria 68 „ 54 „ 



A careful study of the muscular system of the hind limbs, and its meaning and 

 relation to the habits of these birds, would show cause for the various relative lengths 

 of the two regions of the enormously extended ilium ; in the true Gallinaceous birds 

 there is great oscillation, so to speak, in these lengths, as the five figures given by Prof. 

 Huxley show {op. cit. pp. 298-301, figs. 3-7). These figures, and those of the Hoatzin 

 [op. cit. p. 308, figs. 10 & 11), show that there is one remarkable difference between the 

 pelvis of this bird and that of the Alectoromorphse. In the latter the pre-ilia are so 

 united with the sacral spine by ankylosis as to form a right and left gallery, open at 



