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U. S. p. R. R. EXP. AND SURVEYS— ZOOLOGY — GENERAL REPORT. 



List of specimens. 



CENTROCERCUS, Swain son. 



Centrncercus, Sivainson, P. Eor. Am. II, 1831, 49C. Type Teirao urophasianus, Ron. 



Ch. — Tail excessively lengthened, cuneate, longer than the wings, the feathers all lanceolate. Tarsi featliered to tlie 

 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 culnien lietween 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 region.s. 



Comparative measurements. 



CENTROCERCUS UROPHASIANUS, Swain son. 



Sage Cock; Cock of the Plains. 



Tttrao umphasianus, Bonap. Zool. Jour. HI, Jan. 18i8, 214.— Is. Am. Oin. Ill, 1830; pi. xxi, f. 1.— Ib. Mon. 



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



1829, 1.33.— NuTTAi.i., Man. I, 1832, 6G6.— Aui>. Cm. Biog. IV, 1838, 503 ; pi. 371.— Ib. Syn. 



20.';.— Ib. Birds Amer. V, 184i>, lOfi ; pi. 297.— Kkivberrv, Zool. Cal. & Or. Route, Rep. P. R. 



R. .Snrv. VI, iv, 1857, 95. 

 Teirao (Centrncercus) uropUimanus, Sw. F. Bor. Am. II, 1831, 358 ; pi. Iviii- 

 C'c)i(rocercm urophasianus, Jardine, Game birds, Nat. Lib. Birds, IV, 140 ; pi. xvil. 

 ?? Tetrao phaaianellus, Obu. Guthrie's Geog. 2d Am. ed. II, 1815, 317, bused on Lewis & Clark, II, 181. 

 Cock of the plains, Lewis & Ci.ark, II, 180, sp. 2. 



Sp. Ch.— Tail featliers twenty. Above varied with black, brown, and brownish yellow; coverts having all tlie featliera 

 streaked with the latter. Beneath black; the breast white; the upper feathers with spiny shafts; the lower streaked with 

 black; tail coverts witli white tips ; the sides also witli munli white. Lenfjth, 29 ; wing, 11.30; tail, 11. .SO. 



Ilah. — Sage plains of the northwest. 



Tarsi feathered to tlie 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 



