ANATID.E— THE .SWANS, GEESE, AND DUOKS. 105 



g'. Distance from anterior end of nostril to tip of bill much greater 

 than from same point to loral feathers; tail more than twice as 

 long as tarsus. 



11. Charitonetta. (Page 170.) 



/■ . Distance from anterior end of nostril to loral feathering much less 

 than width of bill at base . 



ij. Distance from posterior end of nostril to loral feathers equal to 

 or greater than length of nostril; anterior outline of loral 

 feathering strongly convex. 



12. Histrionious. (Page 171.) 



g\ Distance from aiiler ior end of nostril to loral feathers less than 

 half the length of thi' nostril; anterior outline of loral feather- 

 ing forming a nearly straight line, running obliquely backward 

 and downward from near nostril to corner of mouth. 



13. ClangiUa. (Pago 173.) 



e'. Distance from tip of bill to loral fi.'athers greater than graduation of 

 taU. 



14. Oidemia. (Page 179.) 



<•'. Feathering of forehead or lores reaching anteriorly to or beyond posterior 

 end of nostril . 



13. Somateria. (Page 175.) 

 a'. Tail abnormal, its feathers narrow, \vith very stiflf shafts, their base scarcely hidden 

 by the very short coverts. 



18. Erismatura, (Page 1S4.) 



SrBFA.MiLV MERGING.— The Mergansers. 



A. Serrations of mandible conspicuously tooth-like, and strongly inclined backward at 



tips. 

 IT. Merganser. (Page 187.) 



B. SiTrations of mandible short, blunt, and not distinctly inclined backward at tips. 

 18. Lophodytes, (Pago mo.) 



Subfamily CYGNIN^.— The Swank. 

 Genus OLOB, Wagler. 



Ulor WaoI/. Isis, 1832, 123-1. Type, Ai>as cugnns Linn. 

 (iEN. Chab. Neck very long (longer than the body); bill longer than the head (com- 

 missure longer than the tarsus), widening slightly to the end, the edges straight; basal por- 

 tion of the bill covered by a soft skin extending over the lores to the eye, the upper outline 

 running nearly straight bai;k from the forehead to the upper eyelid, the lower running from 

 the eye obliquely downward, in a nearly .straight line, to the rictus. Nostrils situated a little 

 posterior to the middle of the maxilla, and quite near the culmen; no trace of a knob or 

 caruncle at base of the bill. Lower portion of tin- tibia bare : tarsus much shortt'r than the 

 middle toe (but little longer than the inner), much compressed, covered witli hexagonal 

 scales which become smaller on the sides and behind. Hind toe small, much elevated, the 

 lobe narrow. Tail very short, rounded or graduated, of 20 to 21 feathers. Wings rounded, 

 the seconil and third quills longest; primaries scarcely reaching beyond the ends of the 

 secondaries. Color entirely white, the sexes alike; young pale grayish. 



The two Nortli Aiiieritan species of olor may bf readily dis- 

 tinguished by the foilowiiif;; characters: 

 —14 



