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 21i, to end of claws 22; 

 wing from flexure 10^; extent of wings 34i; tarsus 2, middle toe and claw 

 2|-; hind toe and claw -/j. 



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 ly'g 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 7f ? l° n g> with very numerous minute papillae behind. The oeso- 

 phagus 12 inches long, of a uniform diameter of -f^, until near the lower 

 part of the neck, where it enlarges to j\, again contracts as it enters the 

 thorax, ending in the proventriculus, which is 1-? long, with numerous 

 oblong glandules, about a twelfth in length. Gizzard obliquely elliptical, 

 2i inches across, l T 8 g- in length, its lateral muscles extremely large, the left 

 -£§ in thickness, the right y^; 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 7^ inches long, is 

 slender and nearly uniform in diameter, measuring ~ s across in the duodenal 

 portion, -^ in the rest of its extent; the rectum 3|- inches long, dilated into 

 a globular cloaca 1 inch in length, and of nearly the same diameter. The 

 coeca are 6g long, T f in diameter for 2 inches of their length, enlarged to T 3 2 

 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. 



