This is one of the best marked of the various races that have been discussed (see p. 124). The ground-color of the upper parts is altogether darker than in any of the others, and the streaks are more sharply defined and narrower; the rufous of the rump is of a castaneous, instead of yellowish cast; the wings appear more uniform with the back, owing to the dark color of the latter, and their pale markings have little of that yellowish tinge so noticeable in the others. In the ashy tinge of the lower parts there is a resemblance to _familiaris_ of Europe; but the latter has not the ochraceous crissum so noticeable in the present bird. There is little resemblance to Western and Rocky Mountain specimens of the _C. americana_ and if these are to be considered as separable from the Eastern (which, however, would not, in our opinion, be advisable) they must not be referred to _mexicana_. The Mexican Creeper is introduced here on account of the probability of its occurrence in the Southern Rocky Mountains. HABITS. Mr. Salvin found the Mexican Tree-Creeper by no means uncommon in the pine forests of the upper zone of the Volcan de Fuego. He also observed it frequenting pine-trees in the district of Chilasco, Vera Paz, at about 6,000 feet above the sea. FAMILY TROGLODYTIDÆ.—THE WRENS. CHAR. Rictal bristles wanting; the loral feathers with bristly points; the frontal feathers generally not reaching to nostrils. Nostrils varied, exposed or not covered by feathers, and generally overhung by a scale-like membrane. Bill usually without notch (except in some Middle American genera). Wings much rounded, about equal to tail, which is graduated. Primaries ten, the first generally about half the second. Basal joint of middle toe usually united to half the basal joint of inner, and the whole of that of the outer, or more. Lateral toes about equal, or the outer a little the longer. Tarsi scutellate. The impossibility of defining any large group of animals, so as to separate it stringently and abruptly from all others, is well understood among naturalists; and the _Troglodytidæ_ form no exception to the rule. Some bear so close a resemblance to the Mocking Thrushes as to have been combined with them; while others again exhibit a close approximation to other subfamilies. The general affinities of the family, however, appear to be to the _Turdidæ_, and one of the best characters for separating the two families appears to exist in the structure of the feet.