. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 26 HOUGH. [VOL. I. from the Rocky Mountains (the source of Bigot's specimen) are in my collection.. FIG. 8. MUSCINAE MUSCAEFORMES. Middle tibia with a prominent macrochaeta on its flexor surface . 2 (The male of some European Mesembrinae has no such macrochaeta, but its middle tibiae are elongate and on their flexor surface thickly hairy.) Middle tibiae without such a prominent macrochaeta . 3 Sternopleural macrochaetae 1:2; elbow of fourth vein forming a rounded angle; no orbital macrochaetae, but the geno-vertical plate un

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. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 26 HOUGH. [VOL. I. from the Rocky Mountains (the source of Bigot's specimen) are in my collection.. FIG. 8. MUSCINAE MUSCAEFORMES. Middle tibia with a prominent macrochaeta on its flexor surface . 2 (The male of some European Mesembrinae has no such macrochaeta, but its middle tibiae are elongate and on their flexor surface thickly hairy.) Middle tibiae without such a prominent macrochaeta . 3 Sternopleural macrochaetae 1:2; elbow of fourth vein forming a rounded angle; no orbital macrochaetae, but the geno-vertical plate uniformly beset with minute bristly hairs ; transfrental macrochaetae small and weak, often difficult to see . . Pseudopyrellia Girschner. Sternopleural macrochaetae 1:3; first longitudinal vein ending in the costa at about the middle of the wing; small cross-vein about opposite the end of the first longi- tudinal ; elbow of fourth longi- tudinal not forming an angle but a gentle curve convex toward the hind border of the wing forming an apical cross-vein which is longer than the terminal portion of the fourth vein before its curvature . . Pyrellia Desvoidy Sternopleural macrochaetae varying, i : 3, i : 2, o : i ; if (rarely) i : i then the anterior notably the smaller; first longitudinal vein ending in the costa far beyond the middle of the wing; small cross-vein a long distance basad to the end of the first longitudinal; fourth longitudinal sweeping in a broad curve, convex toward hind border of wing, towards the third, thus forming an apical cross-vein, which, however, in our spe- cies, is not longer than the terminal portion of the fourth vein before its curvature ...... Mescmbrina Macquart Bend of fourth longitudinal forming a rounded angle. Outline of arista as a whole fan-shaped. Sternopleural macrochaetae I : 2. Musca Linnaeus Bend of fourth longitudinal not forming an angle at all, but a gentle curve ............ 4 Antennae separated at their base by a distinct ridge ; S