For more than twenty years I have been endeavoring to complete the synonymy of our moths, and to find out what species were covered by Walker's and Gueneé's descriptions. During this time I have made three trips to Europe, with this object more or less directly in view. Comparatively few of M. Gueneé's species remain unknown to me; and as many of these were collected by Doubleday, the types will probably be found in the British Museum. Mr. Gueneé's descriptions of species are good, and among the best extant, but he does not give structural characters. The microscope lvas not used by him. His genera contained incongruous material. When he had a species that he did not know what to do with, instead of making a new genus for it, which would have assisted the identification of the species, he often made a group of it, under a genus to which it was opposed in every structural feature—and the species in this way was readily over-looked. As, for instance, Leucania Littera.