Nemertea is a phylum of animals also known as ribbon worms or proboscis worms, consisting of 1300 known species. Most ribbon worms are very slim, usually only a few millimeters wide, although a few have relatively short but wide bodies. Many have patterns of yellow, orange, red and green coloration. The foregut, stomach and intestine run a little below the midline of the body, the anus is at the tip of the tail, and the mouth is under the front. A little above the gut is the rhynchocoel, a cavity which mostly runs above the midline and ends a little short of the rear of the body. All species have a proboscis which lies in the rhynchocoel when inactive but everts to emerge just above the mouth to capture the animal's prey with venom. A highly extensible muscle in the back of the rhynchocoel pulls the proboscis in when an attack ends. A few species with stubby bodies filter feed and have suckers at the front and back ends, with which they attach to a host.
Paradrepanophoridae is a family of worms belonging to the order Polystilifera.
Armaueriidae is a family of worms belonging to the order Polystilifera.
Balaenanemertidae is a family of worms belonging to the order Polystilifera.
Buergeriellidae is a family of worms belonging to the order Polystilifera.
Chuniellidae is a family of worms belonging to the order Polystilifera.
Dinonemertidae is a family of worms belonging to the order Polystilifera.
Pachynemertidae is a family of worms belonging to the order Polystilifera.
Siboganemertidae is a family of worms belonging to the order Polystilifera.
Planktonemertidae is a family of worms belonging to the order Polystilifera.
Pelagonemertidae is a family of pelagic nemerteans belonging to the order Polystilifera.
Protopelagonemertidae is a family of worms belonging to the order Polystilifera.
