Dulse (Palmaria palmata)
From Wikipedia, the free encyclopedia
Palmaria palmata (L.) Kuntze, also called dulse, dillisk, dilsk or creathnach, is a red algae (Rhodophyta) previously referred to as Rhodymenia palmata (Linnaeus) Greville. It grows on the northern coasts of the Atlantic and Pacific oceans. It is a well-known snack food, and in Iceland, where it is known as söl, it has been an important source of fiber through the centuries.
The earliest record of this species is of St Columba's monks harvesting it 1,400 years ago.
Dulse grows attached by its discoid holdfast to the stipes of Laminaria or to rocks. It has a short stipe, the fronds are very variable and vary in colour from deep-rose to reddish-purple and are rather leathery in texture. The flat foliose blade gradually expands and divides into broad segments ranging in size to 50 cm long and 30 - 8 cms in width which can bear flat wedge-shaped proliferations from the edge. 
The reference to Rhodymenia palmata var.mollis in Abbott & Hollenberg (1976),is now considered to refer to a different species: Palmaria mollis (Setchel et Gardner) van der Meer et Bird.
Dulse is similar to another seaweed Dilsea carnosa (Schmidel) Kuntze,  Dilsea, however, is more leathery with blades up to 30cms long and 20cms wide. Unlike Palmaria palmata it is not branched and does not have proliferations or branches from the edge of the frond. The older blades may split however.