[4] Arrhenia also includes species formerly placed in the genera Leptoglossum and Phaeotellus and the lectotype species itself has an unusual growth form that would not normally be called agaricoid.

All of the species grow in association with photosynthetic cryptogams such as mosses, including peat moss, and alga scums on decaying wood, and soil crusts consisting of mixes of such organisms.

Typically the fruitbodies of Arrhenia species are grey to black or blackish brown, being pigmented by incrusting melanized pigments on the hyphae.

Arrhenia was named for the Swedish botanist Johan Peter Arrhenius.

As of November 2023[update], the following species are recognised in the genus Arrhenia:[5]