Description:
Flattened, fan-shaped, rather stiff, light brownish-red fronds, to 100 mm high, with long or short stipes arising from a discoidal base. Fronds repeatedly dichotomously lobed, axils wide, apices rounded, margin smooth.

Habitat:
On rocks, shady pools, lower intertidal and subtidal (to ? m), south and west coasts, frequent.

Similar species:
This is a very variable species and ultimately may prove to emcompass several varibale entities. Long-stiped plants with regularly fan-shaped blades occur on Laminaria hyperborea stipes, whilst plants with short stipes and irregular fronds occur in the lower intertidal and shallow subtidal on rock. The intertidal and shallow subtidal species Rhodymenia holmesii arises from stolons, is narrower and has regular fronds often with apical proliferations as does Rhodymenia ardissonei which occurs in deep water and is difficult to discriminate. Phyllophora sicula is thinner, has an expanded base, long, compressed stipes, and fronds that are undivided or have a few divisions. Schottera nicaeensis is also thinner, has but a short stipe and frequently has marginal proliferations.

(In: Seaweed Site - ©Michael D. Guiry - http://seaweed.ucg.ie/descriptions/Rhopse.html)