552 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 103 Family Periscelidae Auxiliary vein rudimentary, ending free (not apically fused with costa or first vein); no costal breaks; anal cell present; firr^t vein ending well distal to basal third of wing ; costa ending at apex of third vein; second antennal segment with one or more dorsal apical bristles, rather long third segment arising from its ventral surface; arista plumose; face strongly receding below, extending laterally below the buccae, narrowed below the antennae by the anterior extension of the eyes (the longest diameter of the latter being oblique) ; bucca extending upward anteriorly, bearing a row of bristles, of which the anterior is placed well above the oral margin; hairs on lateral portions of face; one reclinate orbital bristle; no preapicals on tibiae; postverticals divergent; no presutural dorsocentral; scutellum with four marginal bristles, its disc bare. Genus Periscelis Loew, 1858 I have suggested elsewhere that Microperiscelis Oldenberg (type, Notiphila annulata Fallen) is antedated by the isogenotypic Myodris Lioy and that the genus is scarcely valid. The properties of the new species described here have led me to conclude that Sphyroperiscelis Sturtevant is also best considered a synonym of Periscelis. There are 11 or 12 species of the family known from the world, and five genera are recognized here, even though Myodris and Sphyroperiscelis are not accepted (see list, p. 556). For convenience, the use of broad generic limits is desirable here. If both the names imder considera-tion are retained it will not be easy to fit the new species into any of the available categories, and a new genus will be indicated, giving 8 genera for 12 species. Key to the Nearctic species of Periscelis 1. Mesonotum dull gray, with a brown median stripe; posterior crossvein strong. P. annulata (Fallen) Mesonotum rather shining black; posterior crossvein faint or largely absent-.2 2. Antennal bases about as far from each other as each is from eye; posterior crossvein represented by stumps at each end P. wheeleri (Sturtevant) Antennal bases much nearer each other than to eyes; posterior crossvein complete but faint P. occidentalis, new species Female genitalia: I have described the internal reproductive systems of Periscelis annulata and P. wheeleri (Sturtevant, 1926, p. 7). These species are much alike, and are very different from any other known forms, especially in that they have three chitinized sperma-thecae that are attached directly to a singly common duct. They are also unusual in that the eggs are blackish brown in color.