THE SKELETON IN BIRDS. THE SKULL. 335 



from the rostrum. Huxley uses the term Dromaeognathous 

 to describe this condition. In all other Carinatae the vomers 

 are narrow behind, and the palatines and pterygoids converge 

 posteriorly and articulate largely with the rostrum. Three 

 modifications of this condition are distinguished by Huxley, and 

 termed Schizognathous, -flSgithognathous, and Desmo- 

 gnathous. 



In the Schizognathae the vomers coalesce and form a 

 narrow elongated bone, pointed in front, separating the 

 maxillo-palatine processes of the premaxillae. Waders, fowls, 

 penguins, gulls, some falcons and eagles, American vultures, 

 some herons and many owls have the Schizognathous arrange- 

 ment. In pigeons and sandgrouse there is no vomer, but the 

 other bones have the Schizognathous arrangement. 



In the .flCgithognathae the arrangement is the same as in 

 the Schizognathae, except that the vomers are truncated in 

 front. Passeres, swifts, woodpeckers, humming birds, rollers, 

 hoopoes have this arrangement. 



In the Desmognathae (fig. 60, A) the maxillo-palatine 

 processes approach one another in the middle line, and either 

 unite with the vomers, or unite with one another, hiding the 

 vomers. Thus a more or less complete bony roof is formed 

 across the palate. The vomers in Desmognathae are small or 

 sometimes absent. Ducks, storks, most herons, most birds of 

 prey and owls, pelicans, cormorants, parrots, and flamingoes 

 are Desmognathous. 



The mandible, as in other Sauropsids, consists of a cartilage 

 bone, the articular, and a series of membrane bones, the 

 dentary, splenial, coronoid, angular, and supra-angular, de- 

 veloped round the unossified Meckel's cartilage. The dentaries 

 of the two rami are nearly always fused together, but in 

 Ichthyornis and Archaeopteryx the two rami are but loosely 

 united. There is often a fontanelle between the dentary and 

 the posterior bones, while the angle is sometimes, as in the 

 fowl, drawn out into a long curved process. 



