138 STRUCTURE AND CLASSIFICATION OF BIRDS 



referable to the auditory capsule, and the nasals above and 

 the vomers below to the nasal capsule. The vomers are 

 often paired bones, and near to them are other small and 

 independent ossifications, such as the septomaxillaries (see 

 under Passeres) and the mediopalatines (see under Cuckoos) . 

 Connected with the eye— ossified, indeed, in th-e sclerotic — is 

 the sclerotic ring. 



3. As membranous ossifications connected with or in 

 the neighbourhood of the visceral arches are the pterygoids 

 and palatines of the first arch, and perhaps the quadrato- 

 jugal and jugal, connecting the quadrate with the maxillae. 

 The pterygoids are, as a rule, style-like bones, flat, however, 

 in the penguins, and may or may not articulate with the 

 basis cranii by means of the basipterygoid processes. The 

 palatines may be completely separate from each other, or 

 fused for a greater or less extent. They are broader or 

 narrower, as the case may be. The lower jaw has a number 

 of membranous ossifications ; these are the splenial, dentary, 

 angular, supra- angular, and coronary. On? or two additional 

 elements may be present. 



With these general characters the skull of birds shows a 

 considerable number of differences of minor importance in 

 different families and genera. The first, perhaps, of these 

 in degree of importance — certainly in general estimation, if 

 not actually so — is the series of modifications of the avian 

 palate which were worked out in detail by Huxley, and 

 after him by Paekee, but which had been previous to 

 Huxley's ' well-known paper studied with some degree of 

 success by Coenay.^ 



Huxley distinguished among the palates of birds the 

 following principal modifications : — 



1. DromcBognathism. — This characterises not only the 

 ratites but also the tinamous, and has been indeed the 



' In P. Z. S. 1867. See also paper by Newton, Ibis, 1868, p. 85, and reply, 

 ibid. p. 357. 



- ' Considerations G6n6rales sur la Classiiioatioii des Oiseaux,' &c., Bev. 

 Zool. Soc. Cuvierienne, 1847 ; see also Heeewaoen, Beitrage z. Kenntn. d. 

 KiefergaiMienapparates d. VOgel, Diss. Inaug., Niirnberg, 1889. 



