804 
U. S P. R R. EXP. AND SURVEYS-— ZOOLOGY—GENERAL REPORT. 
List of specimens. 
Catal. 
No. 
Sex. 
Locality. 
Whence obtained. 
Collected by— 
1972 
2733 
3 
9 
North Atlantic_ 
S. F. Baird.. 
J. J. Audubon_ 
_do--__ 
.do. 
------do---------_ 
OIDEMIA, Fleming. 
Oidemia, Fleming, “Philos. Zool. 1822.” Type Anas nigra, Link. 
Ch. —Bill much swollen at base, the terminal portion much depressed and very broad. Nail broad, occupying the termina] 
portion of the bill. Nostrils situated anterior to the middle of the commissure. Feathers of the chin running forwards as far 
as the nostrils. Color black, with or without small patches of white. 
The scoters or black sea ducks, although differing in the character of the hill to a certain 
extent, have yet so close a relationship that it may he questioned whether there is any 
foundation for generic divisions. For greater convenience in indicating these variations in the 
form of the hill, 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. 1 —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. 
Pelionetta, Kaup. 2 —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. P. 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. P. trowbridgii. 
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. 3 —Color entirely black. Bill black on edges and end ; swollen basal 
portion red... 0. americana. 
1 Mclanitta, Boie, Isis, 1822.— Maceranas, Lesson, Man. II, 1828, 414. Type Anas fusca, Linn. 
2 Pelionetta, Kaup, Entw. Europ. Thienv. 1829. Type Anas perspicillata, L. 
3 Oidemia, Fleming, Philos. Zool. 1822. Type Anas nigra, L. 
