258 
GAD WALL DUCK. 
the male, but the speculum fainter. Tail-feathers and their coverts dusky, 
laterally obliquely indented with pale brownish-red, and margined with 
reddish-white. 
Length to end of tail 19? inches, to end of wings 18f, to end of claws 
19J; extent of wings 31; wing from flexure 8?; tail 3f; tarsus Ifi; middle 
toe If!, its claw yV 
In a male, the roof of the mouth is deeply concave, with a prominent 
median ridge, and oblique grooves toward the end. The tongue is 1 inch 
10 twelfths long, fleshy, with a deep longitudinal groove, two lateral series 
of filaments, and a thin broadly rounded tip, as in other Ducks. The oesopha- 
gus, a, b, is 10£ inches long, 
5 twelfths in diameter for 
about four inches, then en- 
larged to 10 twelfths, and 
again contracted as it enters 
the thorax. The proven- 
triculus, b b, is 1 inch and 
2 twelfths long, its greatest 
diameter 8 twelfths. The 
stomach, c d e, is a very 
large and powerful gizzard, 
of an elliptical form, com- 
pressed, 1 inch and 9 
twelfths long, g inches in 
its greatest breadth, or in 
the direction of the lateral 
muscles, of which the right, 
c, is 10 twelfths thick, the 
left, d, 9 twelfths. The 
epithelium is thick and 
rugous ; much thickened 
and forming two roundish, 
flat or slightly concave 
grinding surfaces, opposite 
the muscles. The intestine, 
e f g , is 6 feet 10 inches 
long, wide, its diameter for 
2 feet being 4i twelfths, 
towards the rectum enlarg- 
ing to 6 twelfths. It forms 
first a very long duodenal 
