238 



OSTEOLOGY OF ANSERES. 



The form most common for the mandible to have, as viewed from 

 above, is well exemplified in Glaucionetta, as shown in Fig. 21, which 

 presents this aspect of the bone in the Carrot 



The articular projections lie nearly in the horizontal plane, and each 

 one supports the two concavities for the mandibular foot of the quad- 

 rate. A rather slender intwiued process directed upward and toward 

 the medial plane projects from the inner one. This may present a small 

 pneumatic foramen at its extremity. Beneath either of these articular 

 portions of the mandible, and to the inner side of the angular process, 

 we discover a deep conical fossa, with its apex to the front. 



It is intended for muscular insertion, and is pre- 

 sent, 1 believe, throughout the group. 



The mandible is very imperfectly pneumatic, 

 particularly in the Brant, where the bone some- 

 times, if not always, entirely lacks this condition. 



For the general form assumed by the hyoidean 

 apparatus in these birds the reader is referred to 

 my figure of these parts as they occur in Branta 

 canadensis^ in (Jones's "Key," second edition, ou 

 page 107 (Fig. 72). 



Here we find an elongated elliptical piece in 

 front, of some width, which represents the glos- 

 sohyal and absorbed ceratohyals. It develops a 

 median facet anteriorly for articulation, with a car- 

 tilaginous rod, which passes iuto the soft part of 

 the tongne proper. 



This glossohyal is longitudinally concaved beneath 

 and correspondingly convex above; it articulates 

 with the fused basi-branchials, the first one of 

 which is by far the stouter element, the second 

 almost spiculiform in its dimensions, and produced 

 by a cartilaginous tip behind. 



The thyrohyal elements consist each of the two 

 usual parts, and these greater coruua curl up grace- 

 fully behind the skull, after the fashion of the class 

 generally. 



Without entering upon details, I find after careful comparison of a 

 sufficient number of skulls, that of the Teals, the Blue-winged species 

 (A. discors), more nearly approaches Spatula than any of that genus, 

 while, on the other hand, a very close resemblance is seen to exist be- 

 tween the skull of Spatula and that of the Mallard, the most evident 

 points of difference in these last being the shape of the premaxilla and 

 the more robust type of skull possessed by the Mallard. With but very 

 few exceptions, 1 believe I have shot every species of Duck in this 

 country, vet, at the present writing, 1 regret to say that I have not at 

 hand the skulls of the genera Daiila, Anas strepera, nor Anas penelope, 



Fig. 21. Mandible of 



Olauciom >><< islandica ,- 



from above, adull 



cf ; life size ; from nature. 



