_Chloris_, BOIE, Isis, 1826, 972 (not of Moehring, 1752). (Type, _Parus americanus_.) _Sylvicola_, SWAINSON, Zoöl. Journ. III, July, 1827, 169. (Not of Humphrey, Mus. Calonnianum, 1797, 60; genus of land mollusks.) (Same type.) _Parula_, BONAP. Geog. & Comp. List, 1838. (Same type.) _Compsothlypis_, CABANIS, Mus. Hein. 1850, 1851, 20. (Same type.) GEN. CHAR. In the species of this genus the bill is conical and acute; the culmen very gently curved from the base; the commissure slightly concave. The notch when visible is further from the tip than in _Dendroica_, but usually is either obsolete or entirely wanting. Bristles weak. The tarsi are longer than the middle toe. The tail is nearly even, and considerably shorter than the wing. Color, blue above, with a triangular patch of green on the back; anterior lower parts yellow. Two species—one with three varieties—of this genus, as lately restricted, are known in America, only one, however, has as yet been detected within the limits of the United States. They may be distinguished as follows:— P. americana. Eyelids white. Yellow beneath restricted to anterior half. Two white bands on wing; a dusky collar across the jugulum. _Hab._ Eastern Province of United States, south to Guatemala; Bahamas; Cuba; Jamaica; St. Croix; St. Thomas. P. pitiayumi. Eyelids dusky. Yellow beneath, extending back along sides to the crissum. _Two white bands on wing._ Above plumbeous-blue; lores and eyelids deep black. Abdomen wholly yellow. Wing, 2.20; tail, 1.75. _Hab._ South America from Bogota to Paraguay … var. _pitiayumi_.[34] Above ashy-blue; lores and eyelids scarcely darker. Abdomen wholly white. Wing, 2.35; tail, 2.05. _Hab._ Tres Marias Islands, Western Mexico … var. _insularis_.[35] _Only a trace of white on wings, or none at all._ Above indigo-blue. Wing, 2.10; tail, 1.70. _Hab._ Costa Rica and Guatemala … var. _inornata_.[36] [Line drawing: _Parula americana_, Bonap.] _Compsothlypis gutturalis_, CABANIS (_Parula gut._, BAIRD, Rev. Am. B.), and _Conirostrum superciliosum_, HARTLAUB (_Parula superciliosa_, BAIRD, Rev.), have been referred by later systematists to this genus; but they are much more closely related to _Conirostrum_,—a genus usually assigned to the _Cærebidæ_. The _“P.” gutturalis_ is confined to Costa Rica; but _“P.” superciliosa_ is a species of the table-lands of Mexico, and likely to be detected in Arizona or New Mexico. The characters of this species are as follows:— _Conirostrum superciliosum_, HARTL. R. Z. 1844, 215. Whole dorsal region, including rump, olive-green; rest of upper parts ashy. Anterior half beneath yellow, with a crescentic bar of chestnut-brown across the jugulum; posterior lower parts white, ashy laterally. A conspicuous superciliary stripe of white. Wing, 2.60; tail, 2.10. Parula americana, BONAP. BLUE YELLOW-BACKED WARBLER.