OSTEOLOGY OF BIRDS 



255 



Along its superior border it anchyloses with the frontal and nasal, 

 the sutural trace being- quite distinct in the adult skull ; not so, 

 however, in most of the ducks and geese. 



Many anserine birds seem to possess a slender jugal bar; in the 

 case of the Red-breastecl merganser, its distal end turns abruptly 

 upward to make its articulation with the quadrate. 



This, latter bone has its orbital process widely bifid ; its mastoidal 

 head is double and roundly convex. In Lophodytes the antero- 

 posterior valley dividing this convexity into two facets, is not very 

 deep. 



The facets at its mandibular foot are two in number, placed ob- 

 liquely. They differ considerably in form and position from the 

 same parts as seen in a specimen of a Brant before me. 



Fig. i Skull of Mergus serrator; right lateral view; . natural size. Drawn 

 by the author from specimen 16626, Smithsonian collection 



The sphenotic process is prominent and gradually curves down- 

 ward .along its extent. In most ducks it points downward and 

 forward. 



We find the hinder moiety of the superior orbital periphery 

 rounded off for the lodgment of the nasal gland. The extent to 

 which this is carried varies in the different species of anserine fowl. 



About the center of the interorbital septum there occurs a large 

 fenestra, and the foramina for the exit of the first and second pair 

 of nerves are much larger than necessary for this purpose alone. 

 These openings in the Hooded merganser are relatively, as well as 

 actually, smaller. 



The pars plana is a very thin, curved sheet of bone, which sup- 

 ports in front a crumpled mass of equally attenuated osseous 

 tissue. This latter projects into the upper space of the rhinal 

 chamber, and no doubt plays the part of a turbinated bone. Neither 

 of these outgrowths comes in contact with the inner aspect of the 

 lacrymal bone of the same side. 



