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



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

 attached to this bone. The free end of the vomer underfioors its anterior end. 



In Struthio the form of the pterygoid (PL XLII. fig. 8) closely resembles that of 

 Dromceus: 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 Rhea the pterygoid (PI. XLII. fig. 8) has undergone a very considerable reduction 

 in size, and now takes the form of a w- -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 Dinornithidce, 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 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 Dromceus 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 (PI. XLII. fig. 6) are broad thin lamina?, roughly quadrangular 



2e2 



