Calicium is a genus of leprose lichen lichens. There are different types of Crustose lichens, including endolithic, endophloidic and leprose. Filimentous, byssoid, leprose, and other lichens do not have a cortex (are ecorticate). Leprose lichens have no inner or outer cortex. Leprose lichens consist of crusts without a layered structure. Leprose lichens lack an outer "skin," or cortex. A leprose lichen is a lichen with a powdery or granular surface.