SP. CHAR. Bill slender, the length being .34 from nostril, the depth .25; the upper mandible much swollen at the base; the under yellow. Above and on the sides uniform slate-gray; the upper surface of wings, tail-feathers, and upper coverts dark brownish-rufous; ear-coverts streaked with white. Beneath pure white, with broad triangular arrow-shaped and well-defined spots of slate-gray like the back everywhere, except along the middle of the belly; not numerous on the throat. A hoary spot at the base of the bill above the loral region; axillars nearly white. Length, 6.80; wing, 3.30; tail, 3.50. HAB. Head-waters of Platte and middle region of United States to Fort Tejon and to Fort Crook, California. This species is readily distinguished from _P. iliaca_ by the slaty back and spots on the breast, the absence of streaks above, and the longer claws. From _townsendi_ it differs in having the head, back, sides, and spots beneath slate-colored, instead of dark reddish-brown. The spotting beneath is much more sparse, the spots smaller, more triangular, and confined to the terminal portion of the feathers, instead of frequently involving the entire outer edge. The axillars are paler. The wings and tail are the same in both species. The young bird is quite similar; but the spots beneath are badly defined, more numerous, and longitudinal rather than triangular. There can be little doubt, however, that this bird is a geographical race of _P. townsendi_. HABITS. For all that we know in regard to the habits and general distribution of this species, we are indebted to the observations of Mr. Ridgway, who met with it while accompanying Mr. Clarence King’s geological survey. It was first obtained in July, 1856, by Lieutenant F. T. Bryan, on the Platte River, and others were afterwards collected at Fort Tejon by Mr. Xantus. Mr. Ridgway found the Slate-colored Sparrow at Carson City, during its spring migrations northward, in the early part of March. At this time it was seen only among the willows along the Carson River, and was by no means common. It had the habit of scratching among the dead leaves, on the ground in the thickets, precisely after the manner of the eastern _P. iliaca_. In the following September he again found it among the thickets in the Upper Humboldt Valley. In Parley’s Park, among the Wahsatch Mountains, he found it a very plentiful species in June, nesting among the willows and other shrubbery along the streams. There it was always found in company with the _M. fallax_, which in song it greatly resembles, though its other notes are quite distinct, the ordinary one being a sharp _chuck_. The nest of the two species, he adds, were also so much alike in manner of construction and situation, and the eggs so similar, that it required a careful observation to identify a nest when one was found.