CONTRIBUTIONS FROM THE CRYPTOGAMIC LABORATORY OF HARVARD UNIVERSITY. — XL VII. PRELIMINARY DIAGNOSES OF NEW SPECIES OF LABOULBENIACEAE. — IV. By Roland Thaxter. Received May 6, 1901. Presented May 8, 1901. Additional material illustrating the well-marked generic type de-scribed in a former paper as Mbnoicomyces renders necessary some modification of the original diagnosis, as well as the separation of several species in a second nearly allied genus, which I have called Eumonoico-myces (E. Papuamis being taken as the type), that is well characterized not only by constant differences in the structure of the peculiar anther-idium, but also by reason of certain differences in gross habit which are constant in normal forms of all three of the known species, one of which, E. invisibilis, was formerly placed by me in Mbnoicomyces. EUMONOICOMYCES nov. gen. Receptacle consisting of a basal and subbasal cell ; the latter producing terminally a sterile appendage and laterally a fertile branch (abnormally more than one) the axis of which is coincident with that of the receptacle from which it is not distinguished and consists of a series of superposed cells which may bear a sterile appendage, an antheridium, or an anther-idium and a perithecium ; the three terminal cells usually bearing these organs in the order mentioned. The antheridia consisting of a single stalk-cell, and a single, often obscure, basal cell; the body of the antherid-ium consisting of a series of numerous antheridial cells in four (?) vertical rows which extend obliquely inward and upward, emptying into a com-mon cavity, and replace entirely the two tiers of wall-cells and the anther-idia of Monoicomyces ; the terminal cells growing upward directly to form four unequal sterile terminal appendages, similar to those of Monoicomyces.