I find that unless we use neurational characters to separate the genera of Phycidœ, that it will be impossible to classify the species with accuracy. All characters drawn from the periphery, the appendages of the body, will be found subject to very gradual modifications, but I do not think we can afford to reject any of them, because of their relative want of stability. Indeed the neuration in the Lepidoptera seems to be as useful as in the Diptera, although there are certain cases (as I long ago pointed out with regard to Thyridopteryx) where it varies not only in the species, but in the opposite wings of the same specimen. I think that we must regard as generically distinct from Penmpelia the North American species Pravella, which has 8, instead of 7 veins to the hind wings (see Bull. U. S. Geol. Surv. 4, 694). For this species, the structure of which I have quite fully described, I propose the generic name Meroptera. I also find that our two species, found in Texas and Colorado, and which probably mine the Agave, viz., Bollii and Dentata, are distinct from the European types of Zophodia, to which Prof. Zeller referred Bollii, the type of the new genus Megaphycis. In the structure of the palpi, shape of the wings, greater size and length of body, our two large species differ strongly.