In an adult Male, the tongue is 1 inch 9 twelfths long, has numerous conical papillæ at the base, is deeply grooved along the middle, has two lateral series of bristles, and terminates in a thin rounded lobe, 2 twelfths long. On the middle line of the upper mandible are about ten short conical papillæ, and on each of its margins about 35 lamellæ; on the lower an equal number. The heart is 1 inch 8 twelfths long, 1 inch 2 twelfths broad. The œsophagus, 8-1/2 inches long, is wide, its diameter at the upper part being 1 inch, towards the middle of the neck 1 inch and a quarter. The proventriculus is 1-1/2 inch long; its glandules cylindrical, 1-1/2 twelfths in length, and, as in all other ducks, arranged so as to form a complete belt. The stomach is a powerful gizzard of a roundish form, 1 inch 10 twelfths long, 1 inch 10 twelfths broad, its lateral muscles very large, the right 10 twelfths thick, the left 9 twelfths. In the stomach were various small bivalve shells and much gravel. The cuticular lining longitudinally rugous; the grinding plates 3/4 inch in diameter. The intestine, 5 feet 7 inches in length, has an average diameter of 6 twelfths. The rectum is 7-1/2 inches long, 8 twelfths in diameter. Of the cœca one is 3 inches 4 twelfths long, cylindrical, obtuse, 2-1/2 twelfths in diameter, the other 4-1/2 inches long. The aperture of the glottis is 8 twelfths long, with numerous minute papillæ behind. The trachea presents the same structure as that of the Velvet Duck. Its upper rings, to the number of 9, are very narrow, and continuous with a large bony expansion, 7 twelfths long, and 8 twelfths broad. Beyond this part its diameter is 5 twelfths, gradually diminishes to 3 twelfths about the middle, then enlarges to 5 twelfths. In this part the number of rings is 78. Then comes a roundish or transversely elliptical enlargement, 1 inch 2 twelfths in breadth, 9 twelfths in length, convex before, slightly concave behind, and composed of about 12 united rings. The trachea then contracts to 4 twelfths and presently enlarges to form the inferior larynx, which is large, ossified, but symmetrical. In this space there are 6 distinct rings, and 10 united. The entire length of the trachea is 7-1/2 inches, its rings are all osseous and strong. The contractor muscles are very strong, pass along the sides of the lower dilatation, on which are given off the cleido-tracheals, then continue to the commencement of the inferior larynx, where the sterno-tracheals come off. The bronchial half-rings 25, unossified. The cavity of the nose is very large, being 2 inches long, 1/2 inch in diameter at the lower part, continued narrow in front over the dilatation causing the external protuberance of the base of the bill. The olfactory nerves are of moderate size; the maxillary branches of the fifth pair very large. AMERICAN AVOSET. _RECURVIROSTRA AMERICANA_, GMEL. PLATE CCCXVIII. ADULT MALE, AND YOUNG IN WINTER.