1888.] PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 251 



The .skull in Mergus serrator: Osseous mandibles long and narrow; 

 lacry in o frontal suture persistent; descending process of lacrymai spine- 

 like; interorbital septum largely deficient at its center; mastoidal 

 head of quadrate single; trochlea of mandibular foot of quadrate with 

 their long axes placed nearly parallel with the long axis of the skull; 

 maxillo-palatines for their anterior halves meet 

 in the median line, posteriorly they are pro- 

 duced as distinct cyliudriform processes with 

 free extremities; pterygoids long, of equal 

 width, and concave outward. 



As a rule, in the skull of Ducks, Swans, and 

 Geese the osseous mandibles vary in length, 

 but are always broad aod of a lamellar struct- 

 ure; lacry mo-frontal suture obliterated; de- 

 scending process of lacrymai much expanded, 

 with flat surface directed outward; interorbital 

 septum very rarely shows a small central va- 

 cuity (Glaucionetta) ; mastoidal head of quad- 

 rate usually double; trochlea? of mandibular foot of quadrate with their 

 long axes placed nearly at right angles with the long axis of the skull ; 

 maxillo-palatines fuse in the median line for their entire lengths, no 

 posterior processes; pterygoids short, straight, and much larger an- 

 teriorly than they are at their proximal extremities. 



Fig. 30. Posterior view of skull 

 of liranta canadensis hutchinsii; 

 mandible removed; life size. 

 Same specimen as Fig. 27 ei seq. 



