624 
U. S. P. R. R. EXP. AND SURVEYS—ZOOLOGY—GENERAL REPORT. 
List of specimens. 
Catal. No. 
Sex. 
Locality. 
Whence obtained. 
6 
£ 
to 
*Jh 
o 
Collected by— 
10026 
10025 
9 
S 
St. Mary's, Kocky mountains.- 
Gov. Stevens. 
142 
Lt. Mullen, U. S. A 
CENTROCERCUS, Swains on. 
Centrocercus, Swain son, F. Bor. Am. II, 1831, 496. Type Tetrao urophasianus, Bon. 
Ch.—T ail excessively lengthened, cuneate, longer than the wings, the feathers all lanceolate. Tarsi feathered to the 
joint and between the bases of the toes. Lower throat and its sides with stiffened spinous feathers. Nasal fossae extending 
very far forward ; the length of cuhnen between them two-thirds the total length. Color mottled yellowish above, with large 
black patches beneath. 
The single species of this genus inhabits exclusively the high and almost desert sage plains 
of the far west, feeding on the Artemisia or wild sage which characterises those regions. 
Comparative measurements. 
CENTROCERCUS UROPHASIANUS, Swain son. 
Sage Cock; Cock of the Plains. 
Tetrao urophasianus, Bonap. Zool. Jour. Ill, Jan. 1828,214.—In. Am. Orn. Ill, 1830; pi. xxi, f. 1 .—Ib. Mon. 
Tetrao, in Trans. Am. Phil. Soc. N. S. Ill, 1830, 390 .—Douglas, Trans. Linn. Soc. XVI, 
1829, 133 .—Nuttall, Man. I, 1832, G6G.— Aud. Orn. Biog. IV, 1838, 503 ; pi. 371.— Ib. Syn. 
205.— Ib. Birds Amer. V, 1842, 106 ; pi. 297 .—Newberry, Zool. Cal. & Or. Route, Rep. P. R. 
R Surv. VI, iv, 1857, 95. 
Tetrao ( Centrocercus ) urophasianus, Sw. F. Bor. Am. II, 1831, 358 ; pi. Iviii. 
Centrocercus urophasianus, Jarpine, Game birds, Nat. Lib. Birds, IV, 140 ; pi. xvii. 
?? Tetrao phasianellus, Orv. Guthrie’s Geog. 2d Am. ed. II, 1815, 317, based on Lewis & Clark, II, 181. 
Cock of the plains, Lewis & Clark, II, 180, sp. 2. 
Sp. Ch.—T ail feathers twenty. Above varied with black, brown, and brownish yellow; coverts having all the feathers 
streaked with the latter. Beneath black; the breast white; the upper feathers with spiny shafts; the lower streaked with 
black ; tail coverts with white tips ; the sides also with much white. Length, 29 ; wing, 11.30 ; tail, 11.50. 
Hub .—Sage plains of the northwest. 
Tarsi feathered to the toes, the feathers extending along the sides of the toes at the base. 
Tail elongated, longer than the wings, and excessively cuneate ; of twenty feathers, all lanceo¬ 
late acute and much graduated ; the lateral feathers about four and a half inches shorter than 
