DUSKY DUCK. 251 
is more brown, and has the speculum of the same tints, but without the 
white terminal line. 
Length to end of tail 22 inches, to end of wings 21?, to end of claws 22 ; 
wing from flexure KM ; extent of wings 84? ; tarsus 2, middle toe and claw 
24 ; hind toe and claw 
In this species, the number of feathers in the tail is eighteen, although it 
has been represented as sixteen. In form and proportions the Dusky Duck 
is very closely -allied to the Mallard. The following account of the digestive 
and respiratory organs is obtained from the examination of an adult male. 
On the upper mandible are 43 lamellae ; on the lower, 85 in the upper, 
and 56 in the lower series. The tongue is l-rV inches long, with the sides 
parallel and furnished with a double row of filaments, numerous small conical 
papillae at the base, a median groove on the upper surface, and a thin rounded 
appendage, a twelfth and a half in length, at the tip. The aperture of the 
glottis is 7A long, with very numerous minute papillae behind. The oeso- 
phagus 12 inches long, of a uniform diameter of T V, until near the lower 
part of the neck, where it enlarges to T \, again contracts as it enters the 
thorax, ending in the proventriculus, which is If long, with numerons 
oblong glandules, about a twelfth in length. Gizzard obliquely elliptical, 
2f inches across, 1 X 8 J in length, its lateral muscles extremely large, the left 
•if in thickness, the right T \ ; their tendons large and strong ; the lower 
muscle moderately thick ; the cuticular lining firm and rugous, the grinding 
surfaces nearly smooth. The intestine, which is 5 feet 74 inches long, is 
slender and nearly uniform in diameter, measuring T V across in the duodenal 
portion, r \ in the rest of its extent ; the rectum 34 inches long, dilated into 
a globular cloaca 1 inch in length, and of nearly the same diameter. The 
coeca are 6i long, in diameter for 2 inches of their length, enlarged to 
t 3 3 in the rest of their extent, and terminating in an obtuse extremity. 
The trachea, moderately extended, is 10 inches long. Its lateral or con- 
tractor muscles are strong, and it is furnished with a pair of cleido-tracheals, 
and a pair of sterno-tracheals. The number of rings is 136, besides 12 
united rings forming a large inferior larynx, which has a transversely oblong 
bony expansion, forming on the left side a bulging and rounded sac. There 
are 28 bronchial half rings on the right side, 26 on the left. 
