PHYLOGENY OF THE PAL^OGNATH.^ AND NEOGNATH.^. 207 



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

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



In the Neognathv, 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 ])terygoid extends 

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

 though but l)y the slightest contact. The palatines have succeeded in moving inwards 

 beneath these anterior pterygoid ends so as to all l)ut 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 witli 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 tlie Neognatluv is a 

 secondary feature, the palato-pterj'goid connection in the late embryo not differing 

 materially from that of the Fakcognatha'. Further, the apparent isolation of the 

 vomer from the pterygoid in the Neogiiathw is seen to be a cocnogenetic character, 

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

 Palceognath(e. 



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

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

 ])arasphenoidal rostrum, a change which indicates a shortening both of vomer and 

 rostrum. 



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

 antorbital plate, in the Pahrognatlwi it may reach nearly as far as tlie l>asipterygoid 

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



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

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

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

 region of the antorbital plate. 



Yet other evidences of shifting and modification of the dromgeognathous palate 

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

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

 lower grade of type persistent in the Pahrognatlue. 



In the PaUfognatlim 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 forw^ard shifting of the Neognathine vomer, which we have already noticed — a 



2g2 



