MOEPHOLOGY OF OPISTHOCOMUS CEISTATUS. 57 



narrow nasal processes of the premaxillaries ; in the other two birds the hinge is perfect. 

 In Grax gloMrera the narrowest frontal width is 33 millim., so that relatively, although 

 broad, it is a much narrower skull than that of Coryfliaix or Opisthocomus. Yet, with 

 the exception of Opisthocomus, the skull of this bird is the most Musophagine of all 

 the Gallinaceae. These three types of skull are all holorhinal, but the ossification of 

 the upper face in the strong skull of Crax is much less than in the light skull of 

 Corythaix, or in that of Opisthocomus, which is intermediate in this respect \ 



In Crax gloUcera the external nostrils in the macerated skull are large, obliquely 

 oval spaces, 22 millim. by 12 millim. in size; for the alinasal cartilages that so 

 largely fill this space are lost in such preparations. In Corythaix this space is largely 

 closed by the ossification of those cartilages ; this osseous change takes place in a large 

 number of the Coccygomorphse, in very few Coracomorphae (for instance Gymnorhitm), 

 and in no normal member of the Alectoromorphse. In Opisthocormis this ossification 

 is as complete as in Corythaix ; this is very remarkable, and nelps to stamp this bird as 

 aberrant. The actual nasal opening in this bird is obliquely reniform, with the 

 "hilus" below. In Corythaix it is horizontal, and the hilus of the kidney-shaped 

 hole is above, the opening being modified by the protrusion of an ossified valvular 

 process from the inside. In Ojnsthocomtis the hilus is caused by a process of the 

 alinasal laminae, where it rests on the descending crus of the nasal. In this bird the 

 septum nasi is ossified, but its vertical extent is small, and it is fenestrate ; it is like 

 that of Corythaix, but feebler. In Crax glohicera, with an unusually solid skull, even 

 for a Curassow, the lower part only of the septum nasi is ossified, and, as in Accipi- 

 trine birds and Owls, is ankylosed to the swollen maxillo-palatine ; so that, contrary to 

 rule, this Fowl is desmognathous in a secondary manner (see Huxley, P. Z. S. 1867, 

 p. 433, fig. 15). 



The use of such a taxonomic character as Desmognathism or Schizognathism is 

 very extensive in some groups and very limited in others ; and there is no sharp line of 

 distinction between the two. The most Lacertian palate for openness is that of the 

 Woodpecker; the most modified by intense ossification is that of the Toucan; yet 

 these two types, each specialized to the uttermost, have a postcephalic skeleton, not 

 indeed identical, but extremely similar. Corythaix also, and its relatives, have an 

 intensely ossified fore palate; but this abnormal Curassow — Opisthocomus — which 

 looks at first sight as if it might be a member of the Musophagidae, is as schizognathous 

 as the Woodpecker. The structure of the rest of the palatal part of the face of this 

 aberrant bird will show how far it is removed, not merely from the Musophagidae, but 

 even from the Cracidse. But the Cracidae in the New, and the Megapodidae in the Old 

 Tropics, are the most archaic forms of the Fowl tribe ; the latter are very reptilian in 



^ My meaning as to liyM, in contrast with coarsel)' strong skulls, Tvill be seen at once by anyone who will 

 compare the skull of a Toucan with that of the Cock of the Woods (Tetrao nrogalltis) or that of a domestic 

 Goose. 



