Calicium is a genus of leprose lichens. It is in the family Caliciaceae, and has 40 species.

The sexual reproduction structures are a mass of loose ascospores that are enclosed by a cup shaped exciple sitting on top of a tiny stalk, having the appearance of a dressmaker's pin (called a mazaedium), hence the common name pin lichen. They are also commonly called stubble lichens.

They have been used as indicator species for old growth redwood forests.

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