Approximately 1300 valid, described species of the phylum Nemertea, or ribbonworms, are known worldwide, inhabiting oceans, freshwaters, and land. Current field-work suggests that at least several times this number remain to be named or discovered. Nemerteans are unsegmented worms characterized by a unique and remarkable eversible proboscis. Some are colorful, while others are drab. They range from one millimeter to more than 30 meters long. Some are highly specialized predators while others are more eclectic, with diets that favor other worms, crustaceans, and mollusks. They are poorly known to non-specialists, because most nemerteans live in concealment and are difficult to collect, and because traditional taxonomy focuses significantly on internal anatomy based on histological study, while now we use genetic data extensively. However, many are common, abundant and can be key predators, while the phylum itself is important to understanding evolution of early invertebrate body plans. This site is intended to make these worms less enigmatic. The emphasis is on taxonomy, but the intent is to accommodate all aspects of nemertean biology.