_Certhia palustris_, WILSON, Am. Orn. II, 1810, 58, pl. xii, fig. 4 (Penna). _Troglodytes palustris_, BON. Obs. Wils. 1824, no. 66.—AUD. Orn. Biog. I, 1831, 500, pl. c.—IB. Birds Am. II, 1841, 135, pl. cxxiii.—REINHARDT, Ibis, 1861, 5 (Godthaab, Greenland). _Thryothorus palustris_, NUTT. Man. I, 1832, 439. _Cistothorus (Telmatodytes) palustris_, BAIRD, Birds N. Am. 1858, 364; Rev. 147.—SCLATER, Catal. 1861, 22. _Thryothorus arundinaceus_, VIEILLOT, Nouv. Dict. XXXIV, 1819, 58 (not _Trog. arundinaceus_, VIEILLOT). _Thryothorus arundinaceus_, BON. Consp. 1850, 220. _Telmatodytes arundinaceus_, CAB. Mus. Hein. 1850, 78. HAB. Eastern United States, from the Missouri River; Greenland? REINHARDT; Mexico, and Guatemala? Cordova, SCLATER. Var. paludicola. _Cistothorus palustris_, var. _paludicola_, BAIRD, Rev. Am. B. 1864, 148. _Troglodytes palustris_, NEWB. P. R. Rep. VI, IV, 1857, 80 (Pacific region). _Cistothorus palustris_, COOPER & SUCKLEY, P. R. Rep. X, II, 1859, 190 (W. T.)—COOPER, Orn. Cal. 1. 1870, 75. _Certhia palustris_, LORD, Pr. R. Art. Inst. IV, 117. SP. CHAR. Bill about as long as head. Tail and wing nearly equal. Upper parts of a dull reddish-brown, except on the crown, interscapular region, outer surface of tertials, and tail-feathers, which are almost black; the first with a median patch like the ground-color; the second with short streaks of white, extending round on the sides of the neck; the third indented with brown; the fourth barred with whitish, decreasing in amount from the outer feather, which is marked from the base to the fifth, where it is confined to the tips; the two middle feathers above like the back, and barred throughout with dusky. Beneath rather pure white, the sides and under tail-coverts of a lighter shade of brown than the back; a white streak over the eye. Length, 5.50; wing, 2.08; tail, 2.00. (1,454.) HAB. Pacific Coast and Middle Province of United States. In comparing a series of Marsh Wrens of eastern North America with western, we find that they differ very appreciably in certain characteristics, which may be expressed by the following diagnoses:— Bill lengthened, equal to tarsus. Tail-coverts above and below either perfectly plain, or with very obsolete bands, reduced to obscure spots beneath. Bands on tail broken; scarcely appreciable on the middle feathers … var. _palustris_. Bill shorter than tarsus. Tail-coverts distinctly banded all across. Bands on tail quite distinct; appreciable on the central feathers … var. _paludicola_. The differences between these two races is much more appreciable than those between _Troglodytes ædon_ and _T. “parkmanni”_; the most striking character is the much longer bill of the var. _palustris_.