PHYLOGENY OF THE PAL^OGNATH^ AND NEOGNATH.E. 191 



parasphenoidal rostnim and the basipterygoid processes. The palatine is but loosely 

 attached to this bone. Tlie free end of the vomer undcrfloors its anterior end. 



In Stncthw the form of tlic pterygoid (PI. XLII. fig. 8) closely resembles that of 

 Dromams: the points wherein it differs are points wherein it is also degenerate. 

 It lacks the npstanding vertical plate from its antero-external latend border, and it 

 has fused with the palatine. 



In lihea the pterygoid (PI. XLII. fig. 8) has undergone a very considerable reduction 



in size, and now takes the form of a s -shaped rod. The sliort 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. Yentrally 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 Linornithidce, e. g. Emeus, 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 Emeus possessing a broad ledge along its mesial border. 

 Its relations with the vomer and palatine are practically the same as in Ilhea. 



In Cnjidtm the jjterygoid is rod-like as in llliea, relatively longer, much straighter, 

 and more slender. 



In Aptenjx 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 tlie one side and the orbital process of the quadrate on the other, the 

 pterygoid having the appearance of being " morticed "' in between these two jioints 

 of contact. 



')l\\& palatine '\Vl 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 Dromceus the palatine resembles in form that of Casiiarius. It is, however, 

 fenestrated. Its suturations differ only in that there is no overlapping shelf above 

 the pterygoid, 'lliere is no fusion between pterygoid and palatine as in Cnsuarius. 



In Bhea the palatines (PI. XLII. fig. ti) are broad thin laminte, roughly quadrangular 



2e2 



