ABSTRACT
Kirschsteiniothelia elaterascus, a new species from freshwater habitats, is described. This fungus has all the characteristics of the genus Kirschsteiniothelia including mammiform, black ascomata, cellular pseudoparaphyses, fissitunicate asci, and brown, one-septate, verruculose ascospores with a gelatinous sheath. It differs from all other species in the genus in having an endoascus with a long coiled base that uncoils during ascus dehiscence. Sphaeria aethiops, the basionym of the species that typifies Kirschsteiniothelia, is lectotypified.