Plocamium cartilagineum is a medium-sized red marine alga.

Plocamium cartilagineum is an erect red alga growing to 10 cm in length.

The female cystocarps grow to 1 mm in diameter and are on the margins of the frond.

[1] Common all around the British Isles including Shetland and Channel Islands.

[3]Faeroes and Norway to Senegal, Mediterranean and Canary Isles.