Dr. Cooper found small flocks of this species at Fort Mohave, after March 20, frequenting grassy spots among the low bushes, and a month later they were singing, he adds, much like a Canary, but more faintly. They are presumed to remain in the valley all summer. The eggs, four in number, are of a light bluish-green color, oblong in shape, more rounded at the smaller end than the eggs of the _socialis_, and the ground is more of a green than in those of _S. pallida_. They are marked and blotched in scattered markings of a golden-brown color. These blotches are larger and more conspicuous than in the eggs of the other species. They measure .70 by .51 of an inch. Spizella atrigularis, BAIRD. BLACK-CHINNED SPARROW. _Spinites atrigularis_, CABANIS, Mus. Hein. 1851, 133. _Spizella atrigularis_, BAIRD, Birds N. Am. 1858, 476, pl. lv, f. 1.—IB. Mex. Bound. II, Birds, p. 16, pl. xvii, f. 1.—COOPER, Orn. Cal. I, 210. _Struthus atrimentalis_, COUCH, Pr. A. N. Sc. Phil. VII, April, 1854, 67. SP. CHAR. Tail elongated, deeply forked and divaricated. General color bluish-ash, paler beneath, and turning to white on the middle of the belly. Interscapular region yellowish-rusty, streaked with black. Forehead, loral region, and side of head as far as eyes, chin, and upper part of throat black. Quills and tail-feathers very dark brown, edged with ashy. Edges of coverts like the back. No white bands on the wings. Bill red, feet dusky. Immature birds, and perhaps adult female, without any black on head. Length, 5.50; wing, 2.50; tail, 3.00. HAB. Mexico, just south of the Rio Grande; Fort Whipple, Ariz. (COUES); Cape St. Lucas. This species is about the size of _S. pusilla_ and _S. socialis_, resembling the former most in its still longer tail. This is more deeply forked and divaricated, with broader feathers than in either. The wing is much rounded; the fourth quill longest; the first almost the shortest of the primaries. HABITS. This species is a Mexican bird, found only within the limits of the United States along the borders. But little is known as to its history. It is supposed to be neither very abundant nor to have an extended area of distribution. It was met with by Dr. Coues in the neighborhood of Fort Whipple, Arizona, where it arrives in April and leaves again in October, collecting, before its departure, in small flocks. In the spring he states that it has a very sweet and melodious song, far surpassing in power and melody the notes of any other of this genus that he has ever heard.