Among the Ephemeridae which the senior author reared at Ithaca, N.Y., from 1913-1915, were two very common species of the genus Heptagenia. The nymphs of both of these species are described by Needham in Bulletin 86. N. Y. State Museum, and figured in plate 9. Extensive rearings, about 50 in all, show, however, that the nymph described as Heptagenia sp. 3 and illustrated in Fig. 4 of plate 9, is that of Heptagenia interpunctata, while the nymph described for that species and illustrated in Fig. 3 of plate 9 appears to belong to a new species which we here describe.