This little bird is strictly a western species, and for its discovery and the first description of it, we are indebted to Edward Harris, Esq., of New Jersey, well known as one of the most eminent cultivators of Zoological science in America. It was discovered by Mr. Harris during a visit to the Upper Missouri and Yellow Stone rivers, in company with the late Mr. Audubon, and which was the last journey ever performed by the latter distinguished gentleman. The description, with some valuable observations on other species of the genus _Parus_, was first published in the Proceedings of the Philadelphia Academy, Vol. II. p. 300, (Dec. 1845,) from which we make the following extract: “A single specimen of this bird was procured on the 26th of July on the Yellow Stone river, about thirty miles above its junction with the Missouri. It is evidently a bird of the season, with immature plumage, to which may be attributed the dullness of the black on the head and throat. On comparison of this bird with _P. carolinensis_ and _P. atricapillus_, it will be perceived that, beginning with the smallest bird, the parts which are black, decrease, and the white parts increase in size and intensity, in ascending. In _septentrionalis_ the outer web of the lateral tail-feather is entirely white, except a small portion at the base, where there is a slight tinge of grey next the shaft; and the quills, secondaries and all the tail-feathers are margined more broadly and with a purer white than in the other species. [Illustration: Plate 14 The Northern Chickadee Parus septentrionalis (_Harris_)] “The note of this bird is similar to that of _P. atricapillus_, but its voice more liquid and less harsh and querulous in the utterance. Bill longer and stouter.” This bird has been received at the Philadelphia Academy in a collection made by Mr. Edward M. Kern, while attached as Artist to the exploring party commanded by Col. Frémont in 1846. A very fine specimen is in the collection made by the surveying party under the command of Capt. Stansbury in the vicinity of the Great Salt Lake of Utah, and is noticed in Prof. Baird’s Zoological appendix to Capt. Stansbury’s Report, p. 316. (June 1852.) Our figure is of the size of life, and the plant represented is _Microsperma Bartonioides_, a native of Western America. DESCRIPTION AND TECHNICAL OBSERVATIONS. Genus Parus. Linnæus, Syst. Nat. I. p. 340, (1766.) Parus septentrionalis. Harris, Proc. Acad. Philada., II. p. 300, (1845.) Form. The largest species of typical Parus yet discovered in America. Wing with the fifth primary longest; tail, long, somewhat fan-shaped; tarsi and toes, rather strong; claws, large, flattened, sharp. Dimensions. Total length (of skins) 5½ to 6 inches; wing, 2¾; tail, 2¾ to 3 inches.