Canace. Tail broad, nearly even, or truncate, and rounded laterally, two thirds the wing. Nasal fossæ scarcely half the culmen.
Centrocercus. Tail excessively lengthened and cuneate; longer than the wings. Nasal fossæ two thirds the culmen. Shafts of feathers on the lower throat very spinous.
Pediœcetes. Tail very short, but graduated, and with the two middle feathers (perhaps tail-coverts) lengthened beyond the rest, and two thirds as long as the wing; the next longest half the wing. Nasal fossæ not half the length of culmen. Shafts of throat-feathers normal.
B. Legs feathered to the lower end of tarsus.
Cupidonia. Tail very short, truncate, but laterally graduated; half the wings. Sides of neck with long, pointed, or lanceolate, stiff feathers. Nasal fossæ scarcely one third the culmen.
C. Legs feathered to the claws.
Lagopus. Tail about two thirds the wing, truncate; of sixteen to eighteen feathers. Most species becoming white in winter; none of the other genera exhibiting this peculiarity.
D. Lower half of tarsi bare, with two rows of scutellæ anteriorly.
Bonasa. Sides of neck with a ruff of broad, truncate, soft feathers. Tail very broad, square, as long as the wings.