The lichen genus Tasmidella was initially described as monotypic, with two chemically-defined varieties. It is now found to comprise two species: T. inactiva (Kantvilas et al.) Kantvilas, stat. nov., containing atranorin only, and T. subfuscescens (Hellb.) Kantvilas, comb. nov., containing xanthones only, with the synonyms T. variabilis Kantvilas et al. var. variabilis and Lecidea dracophylli Zahlbr. The former is recorded from Tasmania and New Zealand; the latter occurs in Tasmania, Victoria and New Zealand and is lectotypified. Salient features of Tasmidella and several superficially similar genera are compared. Keywords: Australia, Bacidiaceae, lichenised Ascomycetes, Megalariaceae, New Zealand, Tasmania, Victoria.