Bulbothrix cinerea is a species of lichenized fungi within the family Parmeliaceae. Among other Bulbothrix species, only B. isidiza has isidia combined with an underside which is light coloured. B. isidiza's laciniae are wider, while its thallus is pale, and contains salazinic acid. In turn, B. ventricosa is larger and a black underside and rhizinae. The African species, B. decurtata is an obligately saxicolous lichen, and while similar, it has a dark underside and produces salazinic acid in its medulla. The species' name thus refers to its uncommon dark gray colouration of its thallus.