A new genus of freshwater ascomycetes, Cataractisopora, with three new species: C. aquatica, C. appendiculata and C. viscosa, are described. These fungi occur on decaying wood and possess similar characteristics including coriaceous globose ascomata, wide septate paraphyses, cylindrical asci with a relatively massive refractive apical ring and ascospores with polar chambers and filamentous appendages. Appendage material accumulates within the polar chambers and, on release from the ascus, the ascospore appendage unfurls to form long threads. The appendage material is fibrillar at the ultrastructural level, and is derived from episporial projections at the ascospore tip. Although these three fungi are similar to species of Annulatascus, they are assigned to a new genus – Cataractispora based on their unique appendage ontogeny. Annulatascus bipolaris is also assigned to Cataractispora on the basis of its ascospore appendage ontogeny.