208 ME. W. P. PYCRAFT ON THE MORPHOLOGY AND 



shifting which brings its proximal end more or less immediately under the antorbital 

 plate — appears to have been accompanied by a similar shifting of the palatines, since 

 these no longer are connected with the main body of the pterygoid bone but with its 

 distal end. This, as we have already shown, ultimately fractures and fuses with the 

 palatine, a joint forming at the line of fracture. This connection of the palatine and 

 pterygoid by means of a joint is a point of great difference between Palaeo- and 

 Neognathine skulls. 



In the Tiiiamidce we have an intermediate stage between the Paloeo- and the Neo- 

 gnathce. The vomer is undoubtedly relatively shorter posteriorly than in Rhea, its 

 free end lying midway between the level of the antorbital plate and the basipterygoid 

 processes. The pterygoid has increased in length, so that the vomer and palatine 

 articulate with its distal extremity only. The quadxato-jugal fossa has also increased 

 in length relatively, extending forwards now beyond the level of the antorbital plate 

 as far as the vestigial maxillo-nasal process. 



A careful study of these points will greatly facilitate the conviction that the 

 segithognathous and schizognathous skulls are but modifications of the dromaeognathous 

 type. The desmognathous is a further modification of the schizognathous palate. 



The single-headed otic process of the quadrate in the Palceognathce, upon which 

 so much stress has hitherto been laid, appears to have less importance than the points 

 to which attention has just been drawn, for in Apteryx the otic process is two-headed, 

 as in Neognathoe. 



The Vertebral Column. 

 The memoirs of Owen, Mivart, and T. J. Parker on the vertebral column of the 

 struthious skeleton render it quite unnecessary to do more than briefly comment 

 thereon here. 



a. The Presynsacral Vertebrce. 



All the presynsacral vertebrae of the Paloeognathas are heteroccelous, and all of 

 this region are free except in the Tinamidee, in which certain of the thoracic 

 vertebrae fuse. 



The vertebra? of Dromceus are the least specialized in type ; those of Casuarius are 

 very similar. 



Both in Dromceus and Casuarius the cervical vertebrae are conspicuously shortened 

 antero-posteriorly. In Casuarius the neural spine, traced from the head backwards, 

 undergoes considerable change of form. Anteriorly it is little more tliEii a median 

 tubercle rising from the centre of a flat neural plate. At about the 6th vertebra it 

 sends backwards a pair of low ridges which terminate in a pair of hyperapophyses.. 

 At about the 10th vertebra, the spine has exchanged its <-shape for a transversely 

 crescentic form. This, for the next 4-5 vertebrae, becomes broken across in the middle 



