A specimen of the ferruginous plumage, in the collection of the Philadelphia Academy, is remarkable for the great intensity and uniformity of the rufous; the entire plumage, in fact, being of this color, a fine light tint of which replaces the white below. There is no trace of bars on either wings or tail. In the very large series before me I find in individuals every possible shade between the two extremes described. Over fifty specimens have come under my notice. HABITS. This little Owl claims a place in our fauna on the strength of several specimens taken in Southern Arizona by Captain Bendire. It is a southern bird, found throughout the whole of Mexico, and ranges thence though the whole of South America, except the Pacific coast, as far south as Southern Brazil. In Mexico it is as abundant on the Pacific as on the eastern coast, and is by far the most common Owl of its genus found in that country. Mr. E. C. Taylor states that he found this bird pretty common in Trinidad, where it is said to fly about in the daytime, apparently indifferent to the blazing tropical sun, and is much smaller than any other species of Owl he met with. GENUS MICRATHENE, COUES. _Micrathene_, COUES, P. A. N. S. Philad. 1866, 57. (Type, _Athene whitneyi_, COOPER.) GEN. CHAR. Size very small (the smallest Owl known); head small, and without ear-tufts. Bill and feet weak. Tail short, less than half the wing, even. Nostril small, circular, opening in the middle of the much inflated ceral membrane. Tarsus a little longer than the middle toe, naked, scantily haired, as are also the toes. Four outer quills with their inner webs sinuated; fourth longest. Ear-conch very small, simple, roundish. Bill pale greenish; iris yellow. [Illustration: ½ _Micrathene whitneyi._] This well-marked genus is represented by a single species, found in the Colorado region of the United States, and in Western Mexico. It is the smallest of all known Owls, and has the general aspect of a _Glaucidium_. From the fact that feathers of birds were found in its stomach, we may reasonably infer that it is of exceedingly rapacious habits, like the species of that genus. Species. =M. whitneyi.= Above grayish olive-brown, sprinkled with small, rather obscure, spots of pale rusty, and interrupted by a whitish nuchal collar; outer webs of the lower series of scapulars pure white. Wings spotted with white and pale fawn-color; tail grayish-brown, crossed by five to six narrow interrupted bands of pale fawn-color. Eyebrows and lores pure white; a cravat of the same on the chin. Beneath white, marked with large, rather longitudinal, ragged blotches of pale rusty, mottled with dusky. Bill pale greenish; iris yellow. Length, 5.50–6.25; extent of wings, 14.25–15.25 (measurements of freshly killed specimens). Wing, 4.00–4.40; tail, 1.90–2.30. _Hab._ Fort Mohave, California (April), and Socorro Island, west coast of Mexico. Micrathene whitneyi, COUES. WHITNEY’S OWL.