Bill various: legs short, often placed far behind, adapted for swimming: lower part of the tibia more or less naked: tarsi compressed: toes generally four; the three anterior ones palmated, semi-palmated. or fissopalmated; or all four united: hind toe sometimes wanting.
Bill stout, straight, covered with a thin membranous skin; the tomia armed with lamellce, or with small denticulations; more or less depressed; the tip rounded and obtuse, furnished with a nail: wings moderate: legs placed in or near the equilibrium: feet four-toed, pal-mated; hind toe free, placed high on the tarsus.
Bill as long as, or shorter than the head, higher than broad at the base, subconic; the upper mandible deflected at the tip; the lower one flat and straight, narrower: nostrils a little behind the middle: neck of moderate length; wings tuberculated, or spurred: legs in the equilibrium: tarsi slightly elongated.
(1. Anser). Bill as long as the head; the tips of the lamellae exserted, appearing like sharp teeth.
(2. Bernicla). Bill shorter than the head, somewhat slender; the edges of the mandihles concealing the tips of the lamellae.
(3. Plectropterus). Bill moderate; furnished with a fleshy tubercle at its base: wings armed with spurs.
Bill moderate, of nearly equal breadth throughout, furnished at its base with a knob or fleshy tumour, convex above; the upper mandible deflected at the tip; the lower one flat: nostrils medial: neck very long: legs a little beyond the equilibrium: tarsi short.
** (ANATINAE ) - Hind toe simple: tarsi somewhat round.
Bill shorter than the head, with an elevated tubercle at the base, depressed or concave in the middle, of nearly equal breadth throughout; the upper mandible laterally grooved near the tip, which is slightly recurved: face and lore feathered: nostrils large, oval, a little before the base: tail even.
Bill furnished with an elevated tubercle at the base; the edges of the mandibles sinuated: face and lore covered with a naked warty skin: nostrils round, basal: wings tuberculated.
Bill as long as, or rather longer than the head, simple at the base, broad and depressed generally throughout its whole length, sometimes widening anteriorly: nostrils small, oval, a little before the base: tail more or less acute, sometimes elongated.
(1. Anas). Bill longer than the head, semicylindric at its origin, depressed and very much dilated towards the tip; toraia furnished with long pectinated lamellae, projecting far beyond the margin: tail a little longer than the wings, of fourteen feathers, moderately acute.
(2. Chauliodus). Bill the length of the head, of nearly equal breadth throughout; pectinated lamellae distinct, appearing below the edge of the upper mandible: tail slightly lengthened; the two middle feathers pointed, and rather longer than the others.
(3. Dafila). Bill full as long as the head; the upper mandible of equal breadth throughout; lamellae not projecting beyond the margin: tail of sixteen feathers, elongated, acute.
(4. Boschas). Bill as long as the head, of nearly equal breadth throughout; the denticulations of the upper mandible scarcely projecting beyond the margin: tail of sixteen feathers, moderate, rather acute.
Bill shorter than the head, higher than broad at the base, depressed and narrowing towards the tip; lamellae slightly projecting: nostrils small, oval, a little before the base: tail of fourteen feathers, short, acute.
Bill shorter than the head, as broad as high at the base, towards the tip narrow and contracted: nostrils large, pervious, submedial: head with an occipital crest: tertials ornamented: tail of sixteen feathers, rounded.
*** (FULIGULINAE). - Hind toe with a lobated membrane: tarsi compressed.
Bill swollen and elevated at the base, nearly straight, extending on the forehead, where it is divided by an angular projection of feathers, narrow and obtuse anteriorly, the nail strong and hooked; tomia set with coarse distant lamellae: nostrils small, oval, medial: tail of fourteen feathers.
Bill short, broad, with an elevated tumour at the base, towards the tip much depressed and flattened; the nail obtuse and rounded, slightly deflected; lamellae coarse, widely set, scarcely projecting: nostrils oval, submedial, elevated: tail short, graduated, acute.
Bill as long as the head, simple at the base or very slightly elevated, broad and very much depressed anteriorly, a little dilated towards the tip; upper lamellae not projecting beyond the edges of the mandible: nostrils rather small, oblong-oval, a little before the base: wings and tail short, the latter generally of fourteen acute feathers.
Bill shorter than the head, elevated at the base, much more contracted than in the last genus, and becoming continually narrower towards the tip; lamellae not projecting: nostrils roundish-oval, medial: tail of moderate length, graduated, the feathers semi-acute.
Bill much shorter than the head, rather high at the base, slender, suddenly contracting towards the tip; nail strong and arched; upper lamellae projecting considerably below the edge of the mandible: nostrils large, oblong-linear, a little before the base: forehead high: tail of fourteen feathers; the central pair acute, and very much elongated.
**** (MERGANINAE ).
Bill short or moderate, straight, slender, narrow, approaching to cylindrical; upper mandible high at the base, tapering towards the tip, which is armed with a strong hooked nail; tomia of both mandibles set with acute teeth directed backwards: nostrils oblong-oval, pervious, medial: legs short, placed far behind: tarsi compressed: hind toe lobated: tail of twelve feathers, rounded.