nemertean
noun
ne·mer·te·an ni-ˈmər-tē-ən 
: any of a phylum (Nemertea synonym Rhynchocoela) of often vividly colored usually long dorsoventrally flattened marine worms that typically burrow in the mud or sand along seacoasts
called also ribbon worm
nemertine
ˈne-mər-ˌtīn
adjective or noun 
Word History
Etymology
ultimately from Greek Nēmertēs Nemertes, one of the Nereids
First Known Use
1861, in the meaning defined above