Description: Thallus filamentous, main axis erect, densely branched, cortex formed by down-growing rhizoidal filaments. Erect axes to 8 (or13) cms high and concealed by overtopping laterals.

Habitat: Epilithic or epizoic in the mid-littoral.

Distribution: Widely distributed in the British Isles especially Ireland and Scotland with a northern distribution, less common in Devon, Cornwall and the Channel Islands. Europe: France, Norway, Faroes and Iceland.

Similar Species: All species of Aglaothamnion and Callithamnion appear similar and not easy to identify .

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

iNaturalist: Aglaothamnion sepositum at iNaturalist World Species Observations database.

WoRMS: Aglaothamnion sepositum at World Register of Marine Species. Accepted name: Gaillona seposita (Gunnerus) Athanasiadis, 2016. AphiaID: 1311358.

Classification: Biota; Plantae; Biliphyta; Rhodophyta; Eurhodophytina; Florideophyceae; Rhodymeniophycidae; Ceramiales; Callithamniaceae; Callithamnioideae; Callithamnieae; Aglaothamnion