[Illustration: _Phyllopneuste borealis._] For the purpose of distinguishing this genus from any other North American, it is enough to say that, of the general appearance of the warblers, it has a short spurious first primary, as in the Thrushes, and some _Vireonidæ_. The single species found as yet within our limits resembles at first sight an immature _Dendroica æstiva_, but is easily distinguished by the wing formula, the yellowish stripe over the eye, and the brown tail-feathers. Phyllopneuste borealis, BLAS. ALASKA WILLOW WARBLER. _Phyllopneuste borealis_, BLAS. Ibis, 1862, 69. _Phyllopneuste_, KENN., BAIRD, Trans. Chicago Acad. Sci. I, ii, p. 313, pl. xxx, fig. 2, 1869. SP. CHAR. (Description of specimen No. 45,909.) Plumage in August: above olive-green, with a slight shade of brown on top of head, rather lighter behind; beneath white, tinged with greenish-yellow; more olive on the throat and breast; and more yellow behind, inside the wing and on thighs; axillars purer yellow. A well-marked greenish-yellow line from nostrils over the eye to the nape (extending behind the eye nearly as far as from eye to tip of bill), beneath this an olivaceous streak through the eye, running into the mixed olive and yellowish of the cheeks. Quills and tail-feathers brown, edged with olivaceous; the outer edges of primaries more yellowish than those of secondaries; the greater coverts tipped externally with greenish-yellow, so as to form a distinct band across the wing. Bill rather dark brown; paler beneath. Legs dark olive; toes not sensibly different. Nest probably on ground, and domed. Eggs white, spotted with pink. Spurious quill in length about one fourth the second, which about equals the sixth, or very slightly exceeds it; third and fourth longest; fifth a little shorter. Dimensions (fresh specimen before being skinned): total length, 4.75; expanse of wings, 6.00; wing from carpal joint, 2.50. Dimensions (prepared specimen): total length, 4.60; wing, 2.40; tail, 2.00. Exposed portion of first primary, 0.42; of second, 1.56; of longest (measured from exposed base of first primary), 1.85. Bill: length from above, 0.38; from nostril, 0.29; along gape, 1.55. Legs: tarsus, 0.66; middle toe and claw, 0.55; claw alone, 0.16; hind toe and claw, 0.36; claw alone, 0.20. HAB. Northeast Asia (China, East Siberia); adjacent to Behring’s Straits and Alaska.