Osten Sacken, Lowe’s Monogr. Dip. N. Am. Pt. 1, p. 192. 1862. Beutenmuller, Am. Mus. Nat. Hist. Guide Leaflet No. 16, p. 28, Fig. 59. Reprint from Am. Mus. Jour. Vol. 4, 1904. 14. =Cecidomyia= sp. =Cecidium= nov. Leaf, under side, distal half conic-attenuate from the bulbous or sub-globular proximal half. Covered with long, coarse trichomes, the longest being half the length of the gall. Trichomes brown. Tip of gall generally darker than rest. 3-4 mm. high, 2-3 mm. wide. Cavity sub-spherical somewhat depressed at right angles to axis of gall. Walls relatively thick, especially the proximal part. Apical canal evident in median longitudinal section. Gall attached by short and broad pillar of tissue extending from the leaf into the fleshy base. Gypsum, Ohio, August, on _H. ovata_. Type specimens at Ohio State University. 15. =Cecidomyia= sp. =Cecidium= nov. On leaf, under side, small, conic galls, generally found in pairs closely appressed to each other but not confluent. Distal attenuate ⅓ rather sharply constricted from the sub-globular ⅔ of the gall and generally turned to one side. 2 mm. high, 1½-2 mm. broad at base. Yellowish in color, definitely and constantly pubescent. Interiorly the lining of the sub-globular larval chamber is deep blue-black in color. Walls of medium thickness. Comparatively large region of the base involved in the attachment of the gall. Collected in Hocking County, Ohio, on _H. alba_, July. Type specimens at Ohio State University. 16. =Cecidomyia= sp. On leaf, under side, greatly depressed with central, prominent nipple, 3-5 mm. dia. 1½-2½ mm. thick (vertical dia.) not including nipple. Light green, smooth. Firm fleshy with central sub-spherical larval chamber whose wall is differentiated from the surrounding tissue. Apical canal through nipple evident. This gall first reported and illustrated by Thompson. Thompson, Illus. Cat. Am. Ins. Galls. 1915. p. 56, pl. 13, Fig. 228. A most interesting variant of this form is illustrated in Fig. 16a. If it were not for the large number of intermediate forms found, this one would easily be considered distinct. The region of the chamber surrounded by thick walls has been much reduced, so that only a circular area about the upper part of the chamber has the thick wall projecting from it. This new condition results in the formation of a definite saucer-shaped structure on the distal end of the gall. In some specimens the structure was no longer saucer-shape, but by the ingrowth of the edges it was assuming a spherical form, developing a two-chambered gall. It is natural to suspect that this may have been the mode of origin of the four-double-chambered galls described elsewhere in this paper. That, however, is entirely problematic. 17. =Caryomyia periscoides= Beut.