In var. _mexicanus_ the white of throat is more abruptly defined against the rufous of abdomen than in var. _conspersus_, in which the transition is very gradual. The latter has the secondaries rufous with narrow isolated bars of black; the former has them blackish, _indented_ on lower webs with dark rufous. In _mexicanus_ the feet are very stout, and dark brown; in _conspersus_ they are much weaker, and deep black. All specimens from south of the United States (including Giraud’s type of _Certhia albifrons_) belong to the restricted _mexicanus_, while all from the United States are of the var. _conspersus_. Catherpes mexicanus, var. conspersus, RIDGWAY. CAÑON WREN; WHITE-THROATED ROCK WREN. _Troglodytes mexicanus_, HEERMANN, J. A. N. Sc. 2d ser. II, 1853, 63.—IB. P. R. R. Rep. X, 1859, 41.—CASSIN, Illust. Birds Cal. I, 1854, 173, pl. xxx. _Catherpes mexicanus_, BAIRD, Birds N. Am. 1858, 356 (in part); Rev. III (in part).—COOPER, Orn. Cal. 1, 1870, 66. _Catherpes mexicanus_ var. _conspersus_, RIDGWAY. SP. CHAR. (No. 53,425 ♂, near Fort Churchill, Nevada, December 7, 1867; R. RIDGWAY). Above, brownish-ashy on the anterior, and bright cinnamon-rufous on the posterior half, the two colors shading insensibly together. The anterior, or grayish portion thickly sprinkled with numerous small circular dots of white, each preceded by a smaller speck of dusky; a few of these dots on the rump. Wings with obsolete, ragged, narrow, _isolated_ bars of dusky, these most sharply defined on the secondaries. Tail clear rufous, crossed with about nine very narrow, thread-like, somewhat zigzag bars of black,—these about .02 wide on the middle, and .07 on the outer feather. Beneath, anterior third, pure silky-white, shading insensibly into soft ochraceous on the breast, this soon darkening into deep ferruginous, the color of all the posterior lower parts; the whole of this ferruginous surface, with very obsolete transverse spots of white, each preceded by a narrower dusky one. Length, 5.75; extent of wings, 7.50 (fresh); wing, 2.48; tail, 2.13; culmen, .83; tarsus, .56. Bill deep slate, paler, and with lilaceous tinge, at base of lower mandible; iris umber; tarsi and toes black (fresh colors). HAB. Central region of North America, from boundary of United States northward. Extends up Valley of Colorado. Western Nevada, resident; RIDGWAY. The above characters apply to all specimens of _Catherpes_ from north of Mexico, as substantiated by a sufficient series in the collection. It is a remarkable fact that this northern race should be so much smaller than the Mexican one, especially in view of the fact that it is a resident bird in even the most northern parts of its ascertained habitat.