Gelidium spinosum (S.G. Gmelin) P.C. Silva
Also known as Gelidium latifolium (Greville) Bornet et Thuret
Description: Cartilaginous, crimson to purplish red, 20-60 mm long. Main axes distinctly flattened, often narrower at base, ultimate branches short, often opposite, spine-like or spathulate.
Habitat: Pools in lower intertidal and subtidal, generally in shaded situations, southern and western shores, frequent.
Similar species: Gelidium pulchellum which does not have strongly flattened main axes and occurs higher on the shore.
Key characteristics: Clear pinnate branching, lower-intertidal and subtidal low-light habitats, and distinctly flattened main axis.