78. Bernicla (Brent and Bernicle Geese). Bill shorter than head, higher than broad at base; culmen slightly convex, outline of lower mandible decidedly so, leaving elliptical space displaying lamellæ; nostrils sub-basal; neck feathers less furrowed than in Anser; tail short, rounded; tibia feathered to joint; hind toe short and elevated.
79. Cygnus (Swans). Bill of equal length throughout, furnished with knob at base; nostrils medial; legs short; neck exceedingly long.
SUB-FAMILY ANATIDÆ
Bill of equal width throughout, or broader at the top than at the base, of about the same width as the head; legs short, placed rather behind the middle of the body; hind toe without a pendent membrane; tarsi somewhat round.
80. Tadorna (Sheldrake). Bill with an elevated tubercle at the base, depressed in the middle; nostrils large, pervious; lower portion of tarsus in front with a row of transverse scutellæ.
81. Anas (Mallard, Gadwall). Bill long as head, broad, depressed, sides parallel, sometimes partially dilated, both mandibles with transverse lamellæ on inner edges; nostrils small, oval, lateral, anterior to base of bill; wings rather long, pointed; tail wedge-shaped; legs rather short; hind toe without lobe. Sexes differ in plumage.