OSTEOLOGY OF BIRDS 



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dial one, having perhaps a little freer movement than a true gin- 

 glymoid articulation [see fig. 15]. 



The palatines barely escape resting against the under side of the 

 rostrum of the sphenoid, which passes immediately above them. 

 This is true of all the Anatinae so far as I have seen. 



As to the vomer (v) proper, we find it to be a thin lamella of 

 bone in the median line, supported, as pointed out above, by the rib 

 on its upper margin developed from the ascending processes of 

 the palatines. This portion is carried forward by a thickening of 

 the vomer itself, somewhere beyond its middle, as a protruding 

 spinelike anterior process. 



This spine usually rests in a groove formed by the union of the 

 maxillopalatines behind, though in a skull of a female Mallard be- 

 fore me not only this projection, but a good share of the vomerine 

 plate has fused with this maxillopalatine mass in part, to become 

 immovably connected with it. 



This condition of fusion is very perfect in Netta rufina, 

 and some other forms, while perhaps it is in such species as 

 Spatula clypeata and Somateria mollissima that 

 the contact between the anterior end of the vomer and the maxillo- 

 palatine mass is the least pronounced. 



The lower margin of the vomer is sharp, and the whole plate is 

 gently arched in such a manner as to make the upper edge convex 

 along its continuity, the reverse obtaining below. 



When speaking of the palatines I neglected to invite attention 

 to the small process found on the inner margin of either one of 

 them about opposite the anterior termination of the vomerine plate. 

 This process may sometimes inclose a foramen in the Mallard, but 

 is usually entirely absent in the Hutchins goose and the Whistling- 

 swan . 



Spatula possesses a pterygoid (pt) of the" same general form it 

 assumes in any of the Anatinae. Its shaft is short and straight, 

 while its anterior end is much enlarged, first, by a descending 

 lamina of bone developed - upon it and, secondly, by the large 

 sessile, elliptical facet on its opposite side for articulation with a 

 similar facet on the sphenoidal rostrum. Anterior to this facet 

 the pterygoid develops an upturned process of spinelike dimensions, 

 which, when the bones are in situ, is closely applied to the back side 

 of the ascending process of the palatine. Below this process the 

 pterygoid is deeply and roundly notched to receive a peglike pro- 

 jection on the palatine, which movably fits into it. 



