Mr. Sumichrast describes its nest[29] as very skilfully wrought with spiders’ webs, and built in the crevices of old walls, or in the interstices between the tiles under the roofs of the houses. A nest with four eggs, supposed to be those of this species, was obtained in Western Texas by Mr. J. H. Clark; it was cup-shaped, not large, and with only a slight depression. The eggs, four in number, were unusually oblong and pointed for eggs of this family, and measured .80 by .60 of an inch, with a crystalline-white ground, profusely covered with numerous and large blotches of a reddish or cinnamon brown. So far as the observations of Mr. Ridgway enabled him to notice this bird, he found it much less common than the _Salpinctes obsoletus_, and inhabiting only the most secluded and rocky recesses of the mountains. Its common note of alarm is described as a peculiarly ringing _dīnk_. It has a remarkably odd and indescribably singular chant, utterly unlike anything else Mr. Ridgway ever heard. This consisted of a series of detached whistles, beginning in a high fine key, every note clear, smooth, and of equal length, each in succession being a degree lower than the preceding one, and only ending when the bottom of the scale is reached. The tone is soft, rich, and silvery, resembling somewhat the whistling of the Cardinal Grosbeak. It was often seen to fly nearly perpendicularly up the face of a rocky wall, and was also noticed to cling to the roof of a cave with all the facility of a true Creeper. GENUS THRYOTHORUS, VIEILL. _Thryothorus_, VIEILLOT, Analyse, 1816, 45. (Type, _Troglodytes arundinaceus_, “_Troglodyte des Roseaux_,” VIEILL. Ois. Am. Sept. II, 1807, 55 = _Sylvia ludoviciana_, LATH.) [Line drawing: _Thryothorus ludovicianus_ 7113] GEN. CHAR. Bill compressed, rather slender; height about one fourth the length above. Culmen and commissure gently curved throughout; gonys straight; tip very obsoletely notched. Nostrils in the lower edge of anterior extremity of the nasal groove, narrowly elliptical, overhung by a stiff scale-like roof of the thickened membrane of the upper part of the nasal groove, the crescentic edge rounded. The septum of nostrils imperforate; the posterior part of the nasal cavity with a short septum projecting into it parallel with the central, not perpendicular as in _Microcerculus_. Wings and tail about equal, the latter moderately rounded; the first primary more than half the second, about half the longest. Tarsi rather short, scarcely exceeding middle toe. Anterior scutellæ distinct, rest of each side of tarsi in a continuous plate. Lateral toes equal. The diagnoses of the North American species are as follows:— Species and Varieties.