Description: An inconspicuous but very common lichen. Usually only the dark perithecia, about 0.25mm across, are visible immersed in the shells of limpets and barnacles.

Key Identification Features:

• Tiny black perithecia immersed in shells of barnacles and limpets.
• Exclusively marine.

Original text submitted by Michael J. Simms

Distribution Map from NBN: Collemopsidium halodytes at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Collemopsidium halodytes at iNaturalist World Species Observations database.