PHYLOGENY OF THE PALuEOGNATJLE AND NEOG-NAT1LE. 189 



by some very considerable space. It has assumed a trough-like form, the hollow of 

 the trough closely embracing the parasphenoidal rostrum. On either side the vomer 

 is closely embraced by the maxillo-palatine processes, which fit into specially roughened 

 facets. A similar, but less perfect, arrangement of these parts obtains in the 

 Cassowary. 



If the vomer were produced backwards on the pterygoid we should have a 

 type of palate more nearly resembling that of Casuarius and Dromasus than any 

 other Eatite. 



In Rhea the vomer is cleft posteriorly for rather less than half its length, and is pro- 

 duced anteriorly into two large blade-like laminae, widely separated in the median line, 

 and each terminating in a pointed extremity. These anterior laminae are embraced 

 between the palatine processes of the premaxilla and the maxillo-palatines. The 

 parasphenoidal rostrum appears in the median line, between these processes, 

 terminating at the level of their free anterior ends. In Casuarius, Dromasus, and 

 Strut/do the anterior end of the rostrum is entirely concealed by the vomer. In the 

 two former the free end of the vomer projects far beyond the rostrum, in the latter the 

 free end of this and of the vomer terminate at the same point. The body of the vomer 

 takes the form of a pair of vertical laminae, fused anteriorly, and moulded on to the 

 rostrum, upon which it slides ; the forward anterior horns lie in a horizontal plane ; 

 the feet are obliquely truncated, their external lateral borders sut mating with the 

 pterygoid (PI. XLII. fig. 5). 



The true relations of the vomer to the pterygoid cannot be made out except from 

 a study of the dorsal view ; they will then be seen to be precisely what obtains in 

 Casuarius or Dromasus, the foot of the vomer underlying the anterior end of the 

 pterygoid. This last is in Rhea rod-shaped in form, but the sutural surface is 

 dorso-ventrally compressed and closely applied to the vomer ; at least in young birds, 

 in adults it seems to become less compressed and yet more pointed. In a ventral view 

 of the skull the vomer would appear to suturate with the palatine only and not the 

 pterygoid, the former being apparently thrust in between them. 



Examined from the dorsal surface, however, it will be seen that the palatine — the 

 exact form of which will be discussed presently — underlies the foot of the vomer on 

 either side, and is continued backwards along the pterygoid in the form of a long 

 pointed spur, concealing all but the proximal end of the pterygoid, so that, seen 

 ventrally, as already remarked, the vomer and pterygoid would seem to be shut off one 

 from the other. 



This is a fact of considerable significance, inasmuch as this isolation of the vomer is 

 a point wherein all the Neognatlm appear to agree, and differ from the Palceo- 

 ynathce. But, as I have elsewhere shown, when discussing the palatine of Rhea 

 (p. 206), this is only an apparent difference. 



In Crypturi the vomer is precisely similar in form and proportions to that of Rhea. 

 vol. xv. — paet v. No. 11. — December, 1900. 2 e 



