Description: Thallus grows from a discoid holdfast to form a frond with distinctive pectinate branching. The frond, up to 15 cms long, is generally flattened and the profuse sympodial branching. The final branchlets are comb-like in groups of 2 - 6 in regular sequence, each group alternating with a similar group on the other side. Gametangial and tetrasporangial plants are similar.

Habitat: Common. Epilithic and epiphytic in the lower littoral and sublittoral to 30 m or more.

Distribution: All around the British Isles including the Shetlands. Europe: Mediterranean, Azores, Portugal, Atlantic coast of Spain and France, Norway, Faroes and Iceland. Further afield: Pacific America from Alaska to California, Chile and the Galapagos Islands, Canary Islands and Australia. Widespread in temperate seas.

Similar Species: Sphaerococcus coronopifolius and Callophyllis cristata are similar but do not show the distinctive branching pattern.

Key Identification Features:

• Easily recognised by the "comb-like" final branchlets.

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

iNaturalist: Plocamium cartilagineum at iNaturalist World Species Observations database.

WoRMS: Plocamium cartilagineum at World Register of Marine Species.