The new species Xenolecia cataractarum Fryday is described from Campbell Island. It differs from X. spadicomma, the only other species of the genus, in having much smaller apothecia and ascospores, an olivaceously pigmented epihymenium (brown in X. spadicomma), and a thallus with a non-amyloid medulla and norstictic acid (amyloid medulla and confluentic acid in X. spadicomma). Xenolecia spadicomma is reported here from several localities on the Falkland Islands and three from the Región de Los Lagos, Chile, which are the first reports of this species since its description from Isla Wellington in the south-west of Patagonia in 1868. A full description of X. spadicomma is also provided.

Eight new species of Lecideaceae are described from the southern subpolar region: Bryobilimbia coppinsiana Fryday, a saxicolous species with one septate ascospores (Campbell Island, New Zealand); Immersaria fuliginosa Fryday, with a thallus composed of thalloconidia (Falkland Islands); Lecidea aurantia Fryday, with an orange thallus (Auckland Islands, New Zealand); L. campbellensis Fryday, with an endolithic thallus and apothecia resembling those of a species of Porpidia (Campbell Island); Poeltiaria ochyrae Hertel, which is similar to P. subincongua but with a thick areolate thallus (South Orkney and South Shetland Islands); P. tasmanica Fryday, which is similar to P. urbanskyana but with smaller ascopores (Tasmania); Poeltidea inspersa Fryday with an enolithic thallus and a hymenium with large oil globules (Falkland Islands); and Porpidia vulcanoides Hertel & Fryday with immersed apothecia with a thick margin and large ascospores (SW Chile). Lecidea kalbii Hertel is resurrected from the synonymy of L. mannii Tuck. and treated as a distinct species. The circumscription of genera within the Lecideaceae is also discussed: Poeltiaria is shown to be heterogeneous, and the genera Labyrintha and Notolecidea are reduced to synonymy with Poeltidea and Poeltiaria respectively, and the new combinations Poeltidia implexa (Malcolm et al.) Hertel & Fryday and Poeltiaria subcontinua (Hertel) Hertel & Fryday made. A key to the genera of Lecideaceae s. lat. is provided.

To date, there have only been two endemic species of the lichen genus Porpidia known from the maritime Antarctic. A new endemic species, Porpidia submelinodes Osyczka & Olech, recognized in the South Shetlands and South Orkneys, is described in this paper. The species is primarily characterized by its rusty orange, sorediate thallus, composed of convex, well separated and rounded areoles, and by the absence of lichen secondary products detectable by TLC. The morphology and soralia of this new species correspond to the arctic-alpine and boreal-mountain lichen Porpidia melinodes. The paper also discusses the differences between these two taxa and all Porpidia species reported from Antarctica.

Four new species and one new forma are described in the genus Porpidia. Porpidia flavocruenta Fryday & Buschbom, a member of the P. macrocarpa group that has previously been overlooked for ‘P. flavocoerulescens’, is reported from Austria, the British Isles, Scandinavia, Iceland, and North America (Alaska); P. islandica Fryday, Knoph & Hertel is reported from Iceland and Scotland; and P. pachythallina Fryday and P. striata Fryday from the British Isles only. The sorediate morph of P. superba is described as P. superba f. sorediata Fryday, known from the British Isles, Sweden, Svalbard, and North America (Maine). Variation in P. macrocarpa is discussed and the new combination P. macrocarpa f. nigrocruenta (Anzi) Fryday made. Secondary metabolite production is discussed and the variation in the production of chemosyndromes considered to be more variable than previously reported. The position of several other taxa is discussed and P. herteliana and P. musiva are reduced to synonymy with P. cinereoatra, P. calcarea to synonymy with P. superba, and P. diversa to synonymy with P. contraponenda. However, P. grisea and P. lowiana are provisionally maintained as distinct species from P. tuberculosa and P. cinereoatra respectively, although P. grisea has not been correctly recorded from the British Isles. The typification of Spiloma tuberculosa Sm., the basionym of Porpidia tuberculosa, is discussed and a lectotype proposed; the new combination Porpidia rugosa (Taylor) Coppins & Fryday is made and shown to be the correct name for P. glaucophaea; and Porpidia flavicunda (Ach.) Gowan is used for the esorediate taxon usually known as Porpidia flavocoerulescens because this epithet is to be proposed for rejection as it is considered to be of confused usage. Porpidia hydrophila is shown to be a member of the P. albocaerulescens group. Porpidia lowiana, P. nadvornikiana, and P. thomsonii are recorded for the first time from the British Isles, and P. macrocarpa f. nigrocruenta confirmed as a British taxon. Notes and a key are provided for all the species of the genus that have been reported from the area.