Description:
Cylindrical, reddish to purple brown, softly gelatinous thallus, simple or sparingly dichotomously branched, 2 mm wide, 250 mm long, with discoid base.
Tallo gametofitico - struttura multiassiale. Dai numerosi filamenti assiali (ad accrescimento indefinito) disposti centralmente, si dipartono rami laterali assimilatori molto ramificati (ad accrescimento definito), avvolti da abbondante mucillagine. Lo sporofito di questa specie è microscopico.

Habitat: Summer annual (May or June-September or October) on exposed rocky shores, generally growing on barnacles and limpets in the lower intertidal, locally common on southern and western shores of Britain and Ireland, rare and local on east coasts.

Similar species:
Helminthocladia calvadosii is a relatively rare 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 nearly always is an epiphyte on Polyides rotundus

(In: Seaweed Site - ©Michael D. Guiry - http://seaweed.ucg.ie/descriptions/Nemhel.html)