A new genus of the Hyphomycetes is described on living leaves of Calathea sp., caeté in Tupi and Portuguese, a plant belonging to the family Marantaceae. The new erected genus has been called Bilboque, and the specific name magnificum: The implications which this genus have when compared to other well known genera, like Polythrincium, Cordana and Piricularia are focussed, and in order to clear problems dealing with morphological features of the new genus its characteristics have been shown in four serial sequences of figures by Indian ink, all them by the hand of the writer.