14 CANVASS-BACK DUCK. 
of the liver, proceeds backward beneath the kidneys, is convoluted in 
several large folds, and finally from above the stomach, passes in a di- 
rect course to the anus. Its coats are thick, its inner surface villous, 
and its diameter is considerable, being in the first part of the duodenum 
;;, then for two feet from ;5, to ;4, enlarged again to ,8,, and so con- 
tinuing to the rectum, which is 6 inches long, 4 inch in diameter, and 
ends in an enlargement or cloaca, about an inch in diameter. The 
coeca, which commence at the distance of 6 inches from the anus, are 8 
inches long, slender, 4, in diameter for 3 inches, afterwards about 55,, 
with the extremity obtuse. The cesophagus and stomach contained 
young shoots of Zostera marina, and in the latter were numerous par- 
ticles of quartz. 
The trachea, when moderately extended, measures 10 inches in 
length, and is furnished with strong lateral or contractor muscles, a 
pair of cleido-tracheal, and a pair of more slender sterno-tracheal. Its 
diameter at the upper part is 44 twelfths, it gradually contracts to 33 
twelfths, enlarges to 44 twelfths, and at the distance of 7} inches from 
the upper extremity, forms a dilatation about an inch in length, and 
7, in its greatest diameter, but composed of distinct rings, then con- 
tracts to #;, and ends in a bony and membranous expansion, forming 
on the left side an irregular thin disk, convex towards the right, and 
flattened towards the left where it is membranous. The expansions 
of the trachea are thus similar to those of the Red-breasted Mergan- 
ser, but of less extent; the rings are of equal breadth on both sides, 
but alternately overlap each other, one side being partially concealed 
by the corresponding sides of those above and below it, while the 
other stands exposed. The lower larnyx is formed of ten united rings, 
together with the bony and membranous expansion described. The 
tracheal rings, rather broad and osseous, are 118; the half-rings of the 
bronchi about 16. . 
