Description: Thallus of tufts of much-branched blades erect to 20 cms. Blades to 2.5 mm wide branching irregularly in one plane and with the midrib asymetric, naked on the innerside and well developed on the side away from the main axis.

Habitat: Common. Epilithic and epiphytic in rock pools of the low-littoral and into the sublittoral to 8 m.

Distribution: Widely distributed around the British Isles including the Shetlands and Channel Islands. Europe: Spain, France, Baltic, Norway, the Faroes and Iceland. Greenland. Atlantic coast of North America: Canada, Maine, New Hampshire, Massachusetts and Connecticut.

Similar Species: Apoglossum ruscifolium and Hypoglossum hypoglossoides. Apoglossum has pointed apices to the blades and neither show the young blades to be asymmetric.

Key Identification Features:

• Blades asymmetric at the apicies.

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

iNaturalist: Membranoptera alata at iNaturalist World Species Observations database.

WoRMS: Membranoptera alata at World Register of Marine Species. Accepted name: Membranoptera alata (Hudson) Stackhouse, 1809. AphiaID: 144758.

Classification: Biota; Plantae; Biliphyta; Rhodophyta; Eurhodophytina; Florideophyceae; Rhodymeniophycidae; Ceramiales; Delesseriaceae; Delesserioideae; Membranoptereae; Membranoptera