Wing, 2.70; tail, 2.80; bill, from forehead, .37. _Hab._ Eastern Province United States var. _pusilla_. “Similar, but colors clearer, and bill more robust.” _Hab._ Peten, Guatemala var. _pinetorum_.[1] _II._ _Streak behind the eye blackish. No rufous tinge on side of breast. Egg deep blue, with black dots and streaks round larger end._ 3. S. socialis. Crown bright rufous, not distinctly divided, generally plain. Forehead black, divided medially with white. Streak of black on lore and behind eye. Rump pure bluish-ash. Bill blackish, lower mandible paler. Auriculars deep ash, in strong contrast with pure white of the superciliary stripe and throat; breast without ashy tinge. Dorsal streaks broad. Wing, 2.80; tail, 2.30. _Hab._ Eastern Province of United States var. _socialis_. Auriculars lighter ash, less strongly contrasted with the white above and below; breast strongly tinged with ash. Dorsal streaks narrow. Wing, 3.00; tail, 2.90. _Hab._ Western Province of United States, and table-lands of Mexico var. _arizonæ_. _b._ Crown light grayish-brown, with distinct black streaks; young differing in streaked. Egg deep blue, with black streaks and dots (precisely as in _socialis_). 4. S. pallida. Crown divided medially by a distinct pale stripe; whitish superciliary stripe, and blackish post-ocular streak sharply defined. A dusky sub-maxillary streak. Nape ashy in contrast with the crown and back. Wing, 2.50; tail, 2.40. _Hab._ Plains of United States, from the Saskatchewan southward var. _pallida_. Crown without a distinct median stripe. Markings on side of head not sharply defined. No dusky sub-maxillary stripe, and nape scarcely different from crown and back. Wing, 2.50; tail, 2.60. _Hab._ Middle and western Provinces var. _breweri_. B. Crown not different from the sides of head; no light superciliary stripe. 5. S. atrigularis. Head and neck all round, and rump, uniform dark ash, gradually fading into white on the abdomen; wing-bands indistinct; bill light brownish-red. _Ad._ Lores, chin, and upper part of throat black. _Juv._ without black about the head. (Eggs unknown.) _Hab._ Adjacent portions of Mexico and southern Middle Province of United States (Fort Whipple, Arizona, COUES; Cape St. Lucas, XANTUS). [1] _Spizella pinetorum_, Salvin, Pr. Z. S. 1863, p. 189. (“Similis _S. pusillæ_, ex Amer. Sept. et Mexico, sed coloribus clarioribus et rostro robustiore differt.”) Spizella monticola, BAIRD. TREE SPARROW.