PHYLOGENY OF THE PALZOGNATHA AND NEOGNATH. 191 
parasphenoidal rostrum and the basipterygoid processes. The palatine is but loosely 
attached to this bone. The free end of the vomer underfloors its anterior end. 
In Struthio the form of the pterygoid (Pl. XLII. fig. 8) closely resembles that of 
Dromeus: the points wherein it differs are points wherein it is also degenerate. 
It lacks the upstanding vertical plate from its antero-external lateral border, and it 
has fused with the palatine. 
In Khea the pterygoid (Pl. XLII. fig. 8) has undergone a very considerable reduction 
in size, and now takes the form of a ~\—— -shaped rod. The short upper limb bears 
facets for articulation with the quadrate and basipterygoid processes. The longer is 
laterally twisted around its own axis, and continued forwards till it reaches the 
parasphenoidal rostrum. Ventrally it is grooved. This grooved surface is applied, 
anteriorly, to the superior border of the vomer, and posteriorly to the upper surface of 
the postero-external angle of the posterior extremity of the palatine. Thus the 
posterior end of the palatine comes to underlie the posterior extremity of the vomer. 
In the Dinornithide, e.g. Hmeus, the form of the pterygoid very closely resembles 
that of Rhea. The points wherein it differs are such as must be regarded as repre- 
senting a more primitive condition: the chief of these lies in the greater width dorso- 
ventrally; the pterygoid of Hmeus possessing a broad ledge along its mesial border. 
Its relations with the vomer and palatine are practically the same as in Rhea. 
In Crypturi the pterygoid is rod-like as in Rhea, relatively longer, much straighter, 
and more slender. 
In Apteryx the pterygoid is elongate, laminate, and pointed in front where it rests 
upon and fuses with the vomer. It anchyloses very early and completely with the 
palatine, so that the precise form of the pterygoid as a whole cannot be made out in 
the adults (see p. 204). Proximally, it is tightly wedged in between the basipterygoid 
process on the one side and the orbital process of the quadrate on the other, the 
pterygoid having the appearance of being “‘morticed” in between these two points 
of contact. 
The palatine in Casuarius takes the form of a roughly triangular plate. Its base 
articulates with the pterygoid and vomer, and the anterior half of its outer side with 
the maxilla. Its connection with the pterygoid is by means of an overlapping suture, 
the pterygoid underlying a broad shelf of bone given off from the palatine. The 
vomerine suture is that of a simple apposition of contiguous edges, as also is the 
junction with the maxilla. In the adult the palatine and pterygoid become indistin- 
guishably fused proximally. 
In Dromeus the palatine resembles in form that of Casuarius. It is, however, 
fenestrated. Its suturations differ only in that there is no overlapping shelf above 
the pterygoid. ‘There is no fusion between pterygoid and palatine as in Casuarius. 
In Rhea the palatines (Pl. XLII. tig. 6) are broad thin lamin, roughly quadrangular 
252 
