In structure the Avosets are similar to the Numenii and Totani. In an adult female the tongue is very short in proportion to the length of the bill, being only 1-3/4 inch long, slightly emarginate at the base with a few conical papillæ, slender, tapering to a point, horny on the back, and flattened above. On the palate are two longitudinal series of blunt papillæ. The posterior aperture of the nares is linear, 10 twelfths long, papillate on the edges. The œsophagus is 7 inches and 9 twelfths long, inclines to the right side, and when the neck is bent becomes posterior at the middle, as in the Herons and other long-necked birds; its diameter 5 twelfths at the upper part, dilated to 8 twelfths previous to its entrance into the thorax. The proventriculus is 1 inch long and 7 twelfths in diameter; its glandules cylindrical, 1 twelfth long. The stomach is a gizzard of moderate strength, oblong, 1-1/2 inch in length, 10 twelfths in breadth, its right lateral muscle 4 twelfths thick. Its contents were remains of small shells. Its inner membrane of moderate thickness, hard, longitudinally rugous, and deeply tinged with red. The intestine is 3 feet long, and 4 twelfths in diameter; the rectum 2 inches long; of the cœca one is 2-3/4 inches long, the other 2-1/4, their diameter 2 twelfths. In another individual the intestine is 3 feet 9 inches long; one of the cœca 2-3/4 inches, the other 3; the stomach 1-1/2 by 1-1/12. Its contents small shell-fish and fragments of quartz. The trachea is 6-1/2 inches long; its rings extremely thin and unossified, 140 in number, its diameter 3-1/4 twelfths, nearly uniform throughout, but rather narrower in the middle. The lateral muscles are very thin. The bronchi are short, of about 10 rings. LEAST TERN. _STERNA MINUTA_, LINN. PLATE CCCXIX. ADULT AND YOUNG.