PHTLOGENY OF THE PALCEOGNATHCE AND NEOGNATHCE. 207 



relation to the pterygoid has also changed, for they no longer are connected with its 

 outer border but by this same inward movement have come to underlie it. 



In the Neognathce, the inward movement has attained its maximum, the palatines 

 meeting one another mesially, as we have just remarked, thrusting the vomer forwards 

 in so doing. As a matter of fact, however, as we have already shown in earlier papers 

 [82], this is not altogether the case. In the young bird the pterygoid extends 

 forwards in a spike-like form, much as in Rhea, so as to articulate with the vomer, 

 though but by the slightest contact. The palatines have succeeded in moving inwards 

 beneath these anterior pterygoid ends so as to all but entirely sever the original 

 relations between them and the vomer. 



Later in life (soon after hatching) the severance is complete. At this stage, the 

 anterior end of the pterygoid fractures at a point corresponding with the free end of 

 the palatine. The fracture later becomes a true joint, and the anterior end of the 

 pterygoid resting upon the palatine gradually merges with this bone so as to obliterate 

 all traces of its original existence. Thus the free pterygoid of the Neognathce is a 

 secondary feature, the palato-pterygoid connection in the late embryo not differing 

 materially from that of the Palceognathce. Further, the apparent isolation of the 

 vomer from the pterygoid in the Neognathce is seen to be a ccenogenetic character, 

 so that the palate of this group is brought into close relation with that of the 

 Palceognathce. 



A further point of interest in this comparison between the Palseo- and Neognathine 

 skull is the change which the vomer in the latter has undergone in relation to the 

 parasphenoidal rostrum, a change which indicates a shortening both of vomer and 

 rostrum. 



The vomer in the Neognathce rarely extends backwards beyond the base of the 

 antorbital plate, in the Palceognatlm it may reach nearly as far as the basipterygoid 

 processes. This is an undoubted proof of the shortening of the vomer. 



That the rostrum has also undergone a considerable shortening is shown by the fact 

 that in the Palceognathce it extends forwards for a very considerable distance beyond 

 the level of the lachrymo-nasal fossa, in the Neognathce it commonly ends in the 

 region of the antorbital plate. 



Yet other evidences of shifting and modification of the dromaeognathous palate 

 reveal themselves in the Neognathce when we come to closely compare them, and 

 whilst these show how closely the two groups are related they show still more the 

 lower grade of type persistent in the Palceognathce. 



In the Palceognathce the free ends of the basipterygoid processes articulate with 

 the extreme proximal end of the pterygoid quite close to the articulation with the 

 quadrate. In Neognathce these processes, when present, have shifted forwards on to 

 the rostrum, so as to articulate with the middle of the pterygoid. 



The forward shifting of the Neognathine vomer, which we have already noticed — a 



2g2 



