• Nereis is commonly known as rag worm or clam worm.

• The body is long, slender and dorso-ventrally flattened reaching a length of 5-30 cm.

• The body consists of a distinct head followed by a number of similar segments.

• Head consists of two parts: a roughly triangular anterior lobe, the prostomium and a posterior ring-like portion, the peristomium.

• Sexes separate.