MERGANSER. NATATORES. MERGUS. 381 
during the summer, and in winter regulating its advances to- 
wards the equator by the state of the season. The trachea 
of the male bird differs from that of the Goosander, in having 
but one enlargement, which commences about two inches and 
a half below the glottis, and which, when extended, is up- 
wards of three inches long, and is more than four times the 
diameter of the parts immediately above and below. About 
three inches above the lower larynx the tube becomes much 
flattened, and is formed of eighteen or twenty rings (broad 
and large on the back, but fine and narrow on the front 
view), the spaces between them being covered by a fine mem- 
brane; and this part much resembles the corresponding por- 
tion of the trachea of the Long-tailed Haveld (Havelda gla- 
cialis). ‘The tympanum is very large, and of an irregular 
heart-shape, being formed of two large bony protuberances, 
which, taken together, measure two inches in length by one 
inch and a half in width, and both of which are furnished 
with a lateral drum-like membrane. 
Pate 58. represents the Adult Male of the natural size. 
Bill, from the nape of the forehead to the tip, two inches 
and a quarter long. The sides of the upper, and the 
whole of the under mandible orange ; the culmen black ; 
teeth numerous, conical, acute; those of the upper man- 
dible largest, and pointing backwards. Legs and feet 
orange, inclining to tile-red. Irides arterial blood-red. 
Head, crest, and upper part of the neck glossy green- 
ish-black ; crest composed of long, narrow, loose-web- 
bed feathers, pointing backwards. List on the back 
part of the neck, mantle, part of the shoulders, interior 
scapulars, basal half of the greater wing-coverts, se- 
condary quills, bastard wing, greater quills, and narrow 
border of the long tertials, glossy black. Collar, mid- 
dle part of the feathers forming the shoulder tuft, exte- 
rior scapulars, middle wing-coverts, anterior half of the 
greater coverts, and secondaries, long tertials, belly, and 
General 
descrip- 
tion. 
Maie. 
