Nereididae (formerly spelled Nereidae) are a family of polychaete worms. It contains about 500 – mostly marine – species grouped into 42 genera. They may be commonly called ragworms or clam worms.

Nereididae. Retrieved May, 08 2021, from en.wikipedia.org/wiki/Nereididae.

Nereis vexillosa belongs to the phylum Annelida, a group known as the segmented worms. It is generally iridescent green and can reach 30 cm in length. It can be distinguished by the size of the upper ligules on the notopodia of the posterior region of the body. The upper ligules are much larger than the lower ligules. It is also without a collar-like structure around the peristomium.

Nereis vexillosa. Retrieved November, 05 2021, from en.wikipedia.org/wiki/Nereis_vexillosa.