Seven species of Cliostomum Fr. recorded from Australia are treated. These include the widespread C. griffithii (Sm.) Coppins, the austral C. praepallidum (Müll. Arg.) Kantvilas & Fryday and the Tasmanian endemic C. vezdae Kantvilas, a reinstated name previously subsumed under C. flavidulum Hafellner & Kalb. Three species are described as new: C. latisporum Kantvilas, a corticolous species containing atranorin and gangaleoidin from coastal Tasmania and New South Wales, characterized by pale pink, soon immarginate apothecia, 0.3–0.9 mm wide, non-capitate, unpigmented paraphyses, and relatively wide, 1(–3)-septate ascospores, 9–15 × 4–6 μm; C. litorale Kantvilas, a saxicolous species containing atranorin and confluentic acid, recorded only from Tasmania, with relatively large, usually pale pinkish apothecia, 0.6–1.5 mm wide, non-capitate paraphyses, and 1(–2)-septate ascospores, 9–13 × 4−6 μm; and C. saxatile Kantvilas, a saxicolous species containing atranorin and lecanoric acid, also known only from Tasmania, with dark brown to black apothecia, 0.3–0.5 mm wide, pigmented with Laurocerasi-brown, capitate paraphyses, and 1-septate ascospores, 7–14 × 3–5 μm. The widespread, coastal Australasian species Tylothallia verrucosa (Müll. Arg.) Kantvilas is transferred to Cliostomum, with the additional synonym Catillaria brisbanensis Räsänen. Megalaria variegata (Müll. Arg.) D. J. Galloway, based on a New Zealand type, is a further synonym of Cliostomum griffithii. All species are illustrated and described on the basis of Australian and Tasmanian specimens.

The genus Mycoblastus in cool temperate latitudes of the Southern Hemisphere is reviewed. Eight species are treated in detail: M. bryophilus Imshaug ex Kantvilas sp. nov., from Campbell Island and Tasmania; M. campbellianus (Nyl.) Zahlbr., M. coniophorus (Elix & A.W. Archer) Kantvilas & Elix comb. nov. and M. dissimulans (Nyl.) Zahlbr., all widespread across the austral region; M. disporus (C. Knight) Kantvilas comb. nov., from New Zealand and Tasmania; M. kalioruber Kantvilas sp. nov, from Tasmania; M. sanguinarioides Kantvilas sp. nov., from Tasmania and south-eastern Australia; and M. leprarioides Kantvilas & Elix sp. nov., from south-eastern Australia (Victoria). Notes are provided on many other species of Mycoblastus, including those recognised for the Northern Hemisphere, and those originally described from austral regions but now excluded from the genus. Major characters of the genus are discussed, including thallus morphology and chemistry, apothecial pigments and ascus structure. It is suggested that the genus is heterogeneous and that some of its closest affinities may lie with the family Megalariaceae and the genus Japewia.