Catenella casepitosa (Withering) L.M. Irvine
Aslo known as Catenella repens (Lightfoot) Batters; and Catenella opuntia
Description: Mat of interlaced blackish-purple to brownish fronds, to 20 mm high, irregularly branched, constricted into flattened segments like tiny Prickly Pear cacti, from creeping stolons with discoid attachments.
Habitat: On sheltered shady rocks or soil near high tide level, often beneath Fucus spiralis, generally distributed, abundant.
Similar species: Gelidium pusillum.
Photographs © M.D. Guiry