The genus Theissenia: T. pyrenocrata, T. cinerea sp. nov., and T. eurima sp. nov.

The diagnosis of Theissenia is emended to include taxa that lack a definite central perithecial columella and taxa that feature ascospores with a germ slit. Theissenia cinerea is described as a new species that lacks a perithecial columella; T. eurima is described as a new species with ascospores having a germ slit. The type species, T. pyrenocrata, is redescribed and compared with the new species. The taxonomic position of Theissenia is discussed.