The genus Thuemenella Penz. & Sacc. is revised. The new combinations T. bicolor (Ell. & Ev.) Boedijn, T. cubispora (Ell. & Holw.) Boedijn, T. hirsuta (Ell. & Ev.) Boedijn and the new species T. hexaspora Boedijn are proposed. Descriptions are given of the families Hypocreaceae and Nectriaceae. The genera of the former family are briefly discussed.