- Elongated, segmented, coelomate (true body cavity) worm-like animals.
- Body provided with setae or parapodia for locomotion.
- Well developed digestive system with the alimentary canal open at both the ends.
- Excretory organs called nephridia.
- Sexes united (as in earthworm) or separate (as in Nereis).
- Regeneration quite frequent.
- Aquatic, some terrestrial animals, some living in tubes and some even parasitic.
Examples: Nereis, Earthworms like Pheretima (free-living in soil), Hirudinaria (leech, a parasitic on cattle)