Nemertea is a phylum of invertebrate animals also known as "ribbon worms" or "proboscis worms". Most of the 1,400 or so species are marine, with a few living in fresh water and a small number of terrestrial forms. They live in all marine habitats, and throughout the world's oceans. Alternative spellings for the phylum have included "Nemertini" and "Nemertinea". "Rhynchocoela" is a name used primarily in North America but gradually abandoned since the 1980s.