The Nemerteans Synopsis covers the identification of all 85 species of these worm-like animals. Although most species are marine, several species live on land or in freshwater, and a few are commensal or parasitic. Typically they burrow into soft muddy or sandy sediments, creep among seaweeds or colonial sessile invertebrates, or hide in crevices or beneath rocks.

They are often capable of extreme elongation and contraction, ranging in length from a few millimetres to up to 30 metres. Most, however, are 20-30 cm long. Since most nemertean species are carnivores or scavengers, and many possess voracious appetites, they are also of ecological significance.

Nemerteans are a separate phylum. They do not possess a distinct head. Anteriorly they are mostly pointed, rounded or blunted. The cephalic region of many species bears transverse, oblique or longitudinal furrows, the cephalic grooves or slits. The anterior region also contains the eyes, although many species, at least as adults, do not possess them.

Synopses of the British Fauna is a series of identification guides. Each volume in the series is a detailed account of a group of animals. They bridge the gap between standard field guides and more specialised monograph or treatise. Since 1993 the the Field Studies Council has published these guides on behalf of the Linnean Society.

These volumes are suitable for the lab or field. The editors aim to keep them as user friendly as possible, with technical terminology at a minimum and a glossary of terms. However the complexity of the subject matter makes the books more suitable for the more experienced practitioner.