[2] The genus was circumscribed in 1921 by Finnish lichenologist Edvard August Vainio, with Phylloblastia dolichospora assigned as the type species.

The photobiont component is typically chlorococcoid, featuring green algal cells that are angular-rounded and grouped irregularly or in clusters.

[4] The ascomata, or spore-producing structures, are perithecia, which means they are sessile (not on a stalk) and range from hemispherical to almost spherical in shape.

While paraphyses (sterile filaments within the ascomata) are absent, periphyses (hair-like structures at the mouth of the perithecia) are usually present.

These spores are oblong to cylindrical in shape, with transverse or muriform (divided in all three dimensions) septation, but without constrictions at the septa, and are colourless.