150 STRUCTUIIE AND .CLASSIFICATION OF BIRDS 



FoEBES), while the goatsuckers show both desmognathism 

 and schizognathism among the members of the group. On the 

 other hand schizognathism is not on the taxonomic side 

 sharply marked off from segithognathism. Huxley's defi- 

 nition of the vomer in schizognathous birds was that it is 

 ' pointed in front ; ' this is not the case with many Schizo- 

 gnathse, e.g. Hcematopus, Numenius (cf. below). And, on the 

 other hand, Parker showed that another peculiarity of the 

 segithognathous skull, the union of the vomer with ossified 

 ahnasals, was also found in the ' Turnicomorphae,' a group 

 which for other reasons should be placed among Huxley's 

 Schizognathse, 



It appears, therefore, undesirable to lay too much stress 

 upon the modifications of the palate, as seen in the three 

 groups just discussed, as a basis of classification. 



Huxley defined desmognathism as follows : ' The 

 vomer is often either abortive or so small that it disappears 

 from the skeleton. Where it exists it is always slender and * 

 tapers to one point anteriorly. The maxillo-palatines are 

 united across the middle line either directly or by the 

 intermediation of the ossifications on to the nasal septum.' 



This definition applies perfectly well to the Anseres and 

 Palamedeae, but not to all other groups of birds. 



But there is the form of desmognathism found in the 

 Steganopodes and in the owls and Acoipitres. In the 

 former group there is no desmognathism (in the sense of 

 Huxley) except in Pelecanus. The maxillo-palatines of 

 Phaethon and Fregata (see below) are perfectly free ; in 

 front of them the palate is complete, but that completeness 

 is formed by a union of lateral extensions of the maxillae 

 which are distinct from the rounded maxillo-palatines. In 

 the cormorant, which is admittedly an ally of Phaethon, there 

 appears at first sight to be a true desmognathism, a fusion, 

 that is to say, of the maxillo-palatines. The plates of bone 

 in question are beneath the ends of the palatines, but, instead 

 of running horizontally in the same plane as the palatines, 

 they run obliquely upwards (when the skull is regarded from 

 below). If it were not for i^'reg'ate, these bones might be 



