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U. S. p. E, B. EXP. AND SURVEYS— ZOOLOGY — GENEEAL EEPOET. 



List of specimens. 



CENTROCERCUS, Swainson. 



Centrocercus, Swainson, F. Bor. Am. II, 1831, 496. Type Tetrao urophasittnus, Eon. 



Ch. — Tail 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 stiiFened spinous feathers. Nasal fossae extending 

 very far forward ; the length of culraen between them two-thirds the total length. Color mottled yellowish above, with large 

 black patches beneath. 



The single species of this genus inhahits 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. 



OENTEOCEROUS UROPHASIANUS, Swainson. 



Sage Cock ; Cock of the Plains. 



Tetrao urophmiamis, Bonap. Zool. Jour. Ill, Jan. 1828,214. — Ib. Am. Orn. Ill, 1830; pi. xxi, f. 1. — Ib. Mon. 



Tetrao, in Trans. Am. Phil. Soc. N. S. Ill, 1830, 390.— Douglas, Trana. Linn. Soo. XVI, 



1829, 133.— NoTTALL, Man. I, 1832, 666.— Aud. Orn. Biog. IV, 1838, 503 ; pi. 371.— Ib. Syn. 



205.— Ib. Birds Amer. V, 1843, 106 ; pl.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, Jardine, Game birds, Nat. Lib. Birds, IV, 140 ; pi. xvii. 

 .'? Tetrao phasianellus, Oru. 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.— Tail 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. 



Hab. — Sage plains of the northwest. 



Tarsi feathered to the toes, the feathers extending along the sides of the toes at the hase. 

 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 



