SWANS, GEESE, DUCKS, and MERGANSERS.
Bill straight, with distinct nail at tip of upper mandible. Margins of bill laminated (Merginae serrated). Tarsus reticulated at back, arid generally in front. Ventral tract bare. Desmognathous. Posterior border of breast-bone with a notch (in some a foramen) on each side of keel. Young hatched covered with down, and able to run or swim at once. Cosmopolitan.