nemertean

noun

any of a phylum (Nemertea) of usually very elongate, unsegmented marine worms with no body cavity and with a protrusile proboscis, living mostly in coastal mud or sand; ribbon worm

Etymology: < ModL Nemertea < Gr Nēmertēs, name of a sea nymph < nēmertēs, unerring

adjective

of or belonging to these worms