Description: Thin sheets, up to ca. 20cms across. Pale red (Mediterranean specimens), orange, yellow or ochre. Grey-brown in alcohol, light brown dried. Soft, but difficult to determine as very thin. Oscules numerous and small.

Habitat: On bivalve shells, stones, bedrock and saddle oysters; on Posidonia in the Mediterranean, 45-360m.

Distribution: Channel (Straits of Dover, Roscoff), Shetland, Norway, Sweden, and more generally in the N.E. Atlantic. Mediterranean. Known recently from Firth of Lorne (W. Scotland), N. and S.W. Ireland. Not uncommon.

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

iNaturalist: Plocamionida ambigua at iNaturalist World Species Observations database.