Description: The gametangial plants form erect flat fronds arising from a small discoid holdfast with a very short stipe. The blade expands, with occasional splits, to 50 cms long and almost as wide. It does not normally branch from the margin, but may split. Cystocarps in the medulla if present may give the frond the texture of sandpaper. The tetrasporic phase is encrusting and may expand to 5 cm or more.

Habitat: Rare. The gametangial phase is epilithic in pools at low littoral and the upper sublittoral. The tetrasporic phase (Haematocelis rubens) may be epilithic or epiphytic on Laminaria stipes.

Distribution: Widely recorded in the British Isles from Ireland, Wales, western Scotland and the south-western shores of England and the Channel Islands. Europe: the Mediterranean, Azores, Portugal, Spain, France and Iceland.

Key Identification Features:

• The gametangial phase has broad flat blade, unbranched but with splits. The tetrasporic phase is a crust similar to other crusts and not easily identified.

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

iNaturalist: Schizymenia dubyi at iNaturalist World Species Observations database.

WoRMS: Schizymenia dubyi at World Register of Marine Species. Accepted name: Schizymenia dubyi (Chauvin ex Duby) J.Agardh, 1851. AphiaID: 145673.

Classification: Biota; Plantae; Biliphyta; Rhodophyta; Eurhodophytina; Florideophyceae; Rhodymeniophycidae; Nemastomatales; Schizymeniaceae; Schizymenia