Candelariella blastidiata Yakovchenko sp. nov. is described. This corticolous species is characterized by biatorine yellow apothecia, a grey squamulose thallus with marginal and lower side blastidia, 8-spored asci, and a northern circumpolar distribution. Candelariella subdeflexa has previously been confused with C. blastidiata, but our analyses of phenotypic and DNA sequence data revealed C. blastidiata should be distinguished from C. subdeflexa. A worldwide key for Candelariella species with grey thalli is provided.
