234 



OSTEOLOGY OF ANSERES. 



quite spongy ; in Branta canadensis hutchinsii theyunite with a firm lamel- 

 liform nasal septum that makes a long abutment against the roof of the 

 rhiiial chamber above. This nasal septum is entirely absent in Spatula, 

 and illy developed in Anas carolinensis and the. .Mallard. 



My drawing of the basal view of this Duck illustrates Coues'fl "Key,'' 

 (Fig. 78), where the above points may be compared with advantage. 



In Spatula (and the arrangement, with a few unimportant minor dif- 

 ferences, holds good fur the group) the palatines (pi) are horizontally 

 compressed at their anterior ends, where they form anchylosed schin- 

 dylesial articulations with the premaxilla and maxillaries, as already 

 described. The body of one of these bones is slenderer along its middle 

 length, separated by a wide interval from its fellow, and half the dis- 

 tance from the vomer (v). 



Its -'ascending process" is short, and is carried along the upper vo- 

 merine margin, where it unites with the opposite palatine to form a lon- 



FiG. 18. Hear view of skull of Spatula clypcata. 



Fig 10. Rear view of skull of Glaucionetta, 

 islandica. Both figures lite size, from the speci- 

 mens. Mandibles removed. Letters as before. 



gitudinal, rib-like re-enforcement along the uppet edge of that bone. 

 It is only in this situation that the anserine palatines meet each other. 



The joint that one of these bones makes with the corresponding ptery- 

 goid (pt) is a sort of mortise-and-tenon arrangement that very per- 

 fectly meets the requirements of the parts involved. 



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 Anatidw 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 protuding spine like anterior pro- 

 cess. 



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

 illo-palatines behind, though in the skull of a female Mallard before me 

 not only this projection, but a good share of the vomerine plate has 

 fused with this maxillo-palatine mass in part, to become immovably 

 connected with them. 



