804 U, S p. K E. EXP. AND SURVEYS — ZOOLOGY — GENERAL REPORT. 



List of specimens. 



OIDEMIA, Fleming. 



Oidemia, Fleming, " Philos. Zool. 1822." Type Anas nigra, Linh. 



Ch. — Bill much swollen at base, the terminal portion much depressed and very broad. Nail broad, occupying the terminal 

 portion of the bill. Nostrils situated anterior to the middle of the commissure. Feathers of the chin Tunning forwards as far 

 as the nostrils. Color blackf with or without small patches of white. 



The scoters or black sea ducks, althougli differing in the character of the bill to a certain 

 extent, have yet so close a relationship that it may be questioned whether there is any 

 foundation for generic divisions. For greater convenience in indicating these variations in the 

 form of the bill, I shall at any rate consider the sections as sub-genera of Oidemia. The group 

 Oidemieae of Bonaparte corresponds to Oidemia as characterized above. 



A. Feathers extending forward in the forehead nearly to the posterior border of nostrils, and 

 for nearly or quite half the length of the lateral edge of bill ; nostrils broad and open, 



Melanetta, Boie.i — Feathers extending nearly as far forward on the sides of bill as above, 

 leaving the edges only free from the base. Bill very broad ; nail broad and almost 

 truncate. 



Male. Bill black at base and edges, red at tip ; a small white patch around the 

 eye and large white wing speculum. Female brown, with the white speculum 



on wing; sides of head whitish ; bill black M. velvetina. 



Pblionbtta, Kaup.^ — Feathers not extending on sides of bill at all. Nail pointed 

 anteriorly. Colors black, with a triangular white patch on top of head and another 

 on nape. Bill red, with a rounded black lateral spot at base. 



Patch on top of head large, extending between posterior outline of eyes. Nostrils 

 very open, rather obtuse anteriorly. Frontal feathers extending half the length 



of edge of bill, and to posterior border of nostrils F. perspicillata. 



Patch on top of head much anterior to the eyes and very small. Frontal feathers 

 extending for two-fifths the length of edge of bill, not as far as the nostrils, 

 which are more linear and acute anteriorly than in the last F. troiohridgii. 



B. Feathers of the forehead scarcely extending on the base of bill at all ; the nostrils situated 

 about midway between their anterior border and the tip of bill. Nail rather acute anteriorly. 



Oidemia, Fleming.*— Color entirely black. Bill black on edges and end ; swollen basal 

 portion red 0. americana. 



1 Mdanilia, Boie, Isis, 1822. — Maceranas, Lesson, Man. II, 1828, 414. Type Anasfmca, Linn. 

 TdimeUa, Kaop, Entw. Europ. Thierw. 1839. Type Anas perspk-illata, L. 

 » Oidemia, Fleming, Philos. Zool. 1822. Type Anas nigra, L. 



