An augmented species concept is proposed for Arthonia pepei s. l. based on its finding on the new host genus Myelochroa. A brief description of Burgoa cf. angulosa, first found on Myelochroa and characterized by erumpent and mainly orange grey instead of superficial and whitish bulbils, is given. Plectocarpon diedertzianum, previously known only from India, is recorded from Russia. Lichenostigma alpinum s. l. is first recorded on Myelochroa. To date, 11 species of lichenicolous fungi are known to grow on Myelochroa, one of which was documented only on this host genus. Lichenicolous fungi were detected on 1 % of herbarium specimens of Myelochroa from the south of the Russian Far East. Keywords: Arthonia, biogeography, Burgoa, lichen-dwelling fungi, Plectocarpon, taxonomy.