Male with bristle-feathers on the sides of the neck, on its lower part small, scale-like feathers; a large bare yellow space on each side, capable of being inflated; tail long, graduated, of twenty, stiffish, acuminate feathers. Upper parts light yellowish-brown, variegated with brownish-black, and yellowish-white; primary quills chocolate-brown, thin outer webs, and part of their inner margins mottled with yellowish-white; tail with about ten bands of yellowish-white on the outer webs, which are otherwise variegated like the back, the inner webs nearly plain brown; throat and fore part of neck whitish, longitudinally spotted with brownish-black; a narrow white band across the throat; sides of the neck, and fore part of breast pure white; sides variegated like the back; axillars and lower wing-coverts white; and part of breast and abdomen black; lower tail-coverts brownish-black, largely tipped with white; tibial and tarsal feathers brownish-grey, faintly barred with brown. Female much smaller, and differing in being destitute of the bare skin on the neck, the plumage entirely of ordinary texture, the tail less elongated, with the feathers less narrow; upper parts variegated as in the male, lower dull yellowish-grey, undulated and streaked with dusky; middle of breast brownish-black, lower tail-coverts tipped with white. _Male_, 30, 36. _Female_, 22. Rocky Mountains and Columbia River, northward. Once seen on the Missouri. Abundant. Partially migratory from high to low grounds in autumn and winter. Tetrao urophasianus, Bonap. Amer. Orn. v. iii. pl. 21. Tetrao (Centrocercus) urophasianus. Cock of the Plains, Swains. & Rich. F. Bor. Amer. v. ii. p. 358. Cock of the Plains, Nutt. Man. v. i. p. 666. Cock of the Plains, Tetrao urophasianellus, Aud. Orn. Biog. v. iv. p. 503. 300. 6. Tetrao Phasianellus, Linn. Sharp-tailed Grouse. Plate CCCLXXXII. Male and Female.