2S2 



NEW YORK STATE MUSEUM 



For the hyoidean apparatus in general, I find an elongated ellip- 

 tical piece in front, of some width, which represents the glossohyal 

 and absorbed ceratohyals. It develops a median facet anteriorly 

 for articulation, with a cartilaginous rod, which passes into the 

 soft part of the tongue proper. 



The glossohyal is longitudinally concaved beneath and corres- 

 pondingly convex above ; it articulates with the fused basibranchials, 

 the first one of which is by far the stouter element, the second al- 

 most spiculiform in its dimensions, and produced by a cartilaginous 

 tip behind. 



The thyrohyal elements consist each of the two usual parts, and 

 these greater cornua curl up gracefully behind the skull, after the 

 fashion of the class generally. 



There is nothing peculiarly characteristic in either the " ear 

 bones " of any of the ducks, or in the circlet of sclerotic osseous 

 platelets of the eyeballs. I have examined both. The sclerotals in 

 O. perspicillata for either eye number between 20 and 24, 

 and have the form usually seen among birds. They are of moder- 

 ate size only, and closely overlap each other, with their interior 

 edges turned outward. The diameter of the external circle their 

 edges form measures 14 millimeters, that of the internal one being 

 9 millimeters. Other species have them in proportion according to 

 size, but in none of the true ducks are the eyes very large as com- 

 pared with the size of their possessors. The orbital cavities, as a 

 rule, are well circumscribed, owing to the thorough ossification of 

 the interorbital septum ; the great development of the lacrymal 

 bones, and the postfrontal processes ; and to the breadth of the 

 pterygoids beneath. In some ducks, however, where these parts 

 show no special high development or unusual size, they have their 

 orbital cavities no better off, in so far as bony protecting walls are 

 concerned, than many other birds. In any duck again, the 

 least shielded parts of an orbit are the roof and the anterior wall, 

 because in the latter the pars plana never appears to be preformed 

 in bone, and in the former protection is lacking due to the marked 

 narrowness of the interorbital frontal region upon the superior 

 aspect of the skull. 



Remainder of the axial skeleton. The general characters of 

 the vertebrae as they are exhibited by most ducks are very well 

 shown in Spatula. 



The atlas has its cup perforated by the odontoid process of the 

 axis, and in it the lateral canals arc completely surrounded by bone, 



