Nemalion helminthoides (Velley) Batters
Also known as Nemalion multifidum.
Description: Cylindrical, reddish to purple brown, softly gelatinous thallus, simple or sparingly dichotomously branched, 2-3 mm wide, 250 mm long, with discoid base.
Habitat: Summer annual (May or June-September or October) on exposed rocky shores, generally growing on mussels (above) barnacles and limpets in the lower intertidal, locally common on southern and western shores, rare and local on east coasts.
Similar species: Helminthocladia calvadosii (Lamouroux ex Duby) Setchell, not included here, is a very rare shallow subtidal species found on western and southern shores. It is generally larger and broader than Nemalion and more profusely and irregularly branched. Helminthora divaricata is more profusely branched and is generally an epiphyte on Polyides rotundus.