Length (of skin) about 4¼ inches. Head and neck above and large space on the throat black, cheeks and sides of the neck white. Entire plumage of the body above cinereous, slightly tinged with brownish olive, below ashy white tinged with brownish. Bill and feet dark. Sexes alike. Hab. Middle and Southern States of North America. Spec. in Mus. Acad. Philada. Obs. Very similar to the preceding, but easily recognized by its smaller size. 3. Parus septentrionalis. Harris, Proc. Acad. Philada. II. p. 300, (Dec. 1845.) The long-tailed chickadee. Length (of skin) about 6 inches. Head above and space on the throat black, cheeks and sides of the neck white. Entire plumage of the body above cinereous, strongly tinged with reddish brown, below ashy white, tinged with yellowish brown, especially on the sides and flanks, external web of outer tail feathers nearly pure white. Bill and feet dark. Tail comparatively longer than in either of the preceding species. Hab. Missouri and the Rocky Mountains. Great Salt Lake. Spec. in Mus. Acad. Philada. and in the National Collection, Washington city. Obs. A species related to, but quite distinct from either of the preceding. It is larger, and the specimens which I have seen have the bill longer and more pointed, the tail much longer, the black space on the head more restricted, and the general coloring more tinged with brown. The white outer edges of the external tail feathers is a well-marked character. 4. Parus montanus. Gambel, Proc. Acad. Philada. I. p. 259, (April, 1843.) Length (of skin) about 5 inches. Head and neck above, line through the eye, space on the throat and upper part of the breast black. Line over the eye, large space on the cheeks and side of the neck white. Body above cinereous, below ashy white tinged with brownish on the flanks, bill and legs dark. Hab. California. Spec. in Mus. Acad. Philada. Obs. This western species is readily distinguished from all others of North America by the broad white line over the eye. Its bill is longer than in the typical species. 5. Parus hudsonicus. Forster, Philosoph. Trans. lxii. p. 430, (London, 1772.) Length (of skin) about 5 inches. Head and neck above deep ferruginous brown, large space on the throat brownish black, cheeks white. Body above brownish cinereous, below ashy white, sides and flanks deep reddish chestnut brown, bill and feet lead colored. Sexes very similar. Hab. British America, and Northern States of the Union. Spec. in Mus. Acad. Philada. Obs. Quite a distinct and well-marked species, erroneously supposed by some European writers to be the young of _P. atricapillus_. It has been found breeding in the State of Maine, by our friend Dr. Brewer of Boston. 6. Parus rufescens. Townsend Jour. Acad. Philada. vii. p. 190, (1837.)