Description: A thin sheet typically 4mm thick which covers rock surfaces in patches 15cm or more in diameter. Yellow to pale orange. Difficult to determine in thin sheet. Oscules are inconspicuous, with slightly raised transparent margins. The large hole in the photograph is really a dead barnacle although oscules are associated with it.

Habitat: Common on vertical rock faces in exposed places; under boulders in rapids - seems to favour strong water movement. Frequently associated with Alcyonium digitatum and Corynactis viridis. "Found growing on Pecten."

Distribution: "British Isles (type locality is Hastings); France; Spain." Known recently from Lough Hyne; N. coast of Donegal; N. coast of Co. Antrim; Calf of Man; St Kilda; Lundy.

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

iNaturalist: Microciona spinarcus at iNaturalist World Species Observations database.