Ophioparma ventosa (L.) Norman forma subfestiva
Haematomma ventosa (L.) A. Massal.
Chemoform devoid of usnic acid with a whitish thallus. May come in mixture with the yellowish form containing usnic acid: Ophioparma ventosa forma ventosa.
Do not confuse with Haematomma ochroleucum var. porphyrium with a thin, powdery thallus and smaller apothecia.