A new species, Halecania ahtii, is described and illustrated. It is only known from the type locality in the Russian Far East. It is characterized by thin, very inconspicuous thallus consisting of small, dispersed areoles and most likely containing argopsin (identifi ed by fast orange-red reaction with P), as well as relatively small ascospores, and a lichenicolous habit on diff erent saxicolous host species on acidic rocks. A key for Halecania species containing argopsin is proposed. Keywords: biodiversity, Primorye Territory.