Abstract
Biatoraalnetorum S. Ekman & Tønsberg, a lichenised ascomycete in the family Ramalinaceae (Lecanorales, Lecanoromycetes), is described as new to science. It is distinct from other species of Biatora in the combination of mainly three-septate ascospores, a crustose thallus forming distinctly delimited soralia that develop by disintegration of convex pustules and the production of atranorin in the thallus and apothecia. The species is known from the Pacific Northwest of North America, where it inhabits the smooth bark of Alnusalnobetulasubsp.sinuata and A.rubra. Biatoraalnetorum is also a new host for the lichenicolous ascomycete Sclerococcumtoensbergii Diederich.