Mastocarpus stellatus

Mastocarpus stellatus (Stackhouse) Guiry, also called Clúimhín Cait [Cats' Puff], Carragheen, or Carrageen Moss, is closely related to Irish Moss, or Chondrus crispus. It is collected in Ireland and Scotland, together with Chondrus crispus as Irish Moss, dried, and sold for cooking and as the basis for a drink reputed to ward off colds and flu. The fronds are channelled unlike those of Chondrus crispus, and it has a curved stipe whereas Chondrus has a flat one. It occurs commonly on rocks in the mid- and lower-intertidal.

M. stellatus is able to coexist with C. crispus on the northern New England coast despite being a competitive inferior to C. crispus. A greater tolerance for freezing allows it to exist above C. crispus in northern environments where freezing stresses are significant. Mastocarpus is rarely found south of Cape Cod on the United States Atlantic coast because it is out competed by Chondrus when the freezing tolerances are lower.

Distribution
Generally common on all coasts of the British Isles save parts of the east of England - Lincoln, Norfolk and Suffolk.