Nereis is a genus of polychaete worms in the family Nereididae. It comprises many species, most of which are marine. Nereis possess setae and parapodia for locomotion. They may have two types of setae, which are found on the parapodia. Acicular setae provide support. Locomotor setae are for crawling, and are the bristles that are visible on the exterior of the Polychaeta. They are cylindrical in shape, found not only in sandy areas, and they are adapted to burrow. They often cling to seagrass (posidonia) or other grass on rocks and sometimes gather in large groups. They are dangerous to touch giving very painful long lasting burns. Nereis worms are commonly known as rag worms or clam worms. The body is long, slender, and dorso-ventrally flattened, reaching a length of 5-30 cm. The head consists of two parts: a roughly triangular anterior lobe—the prostomium—and a posterior ring-like portion—the peristomium. The latter bears a pair of terminal tentacles, dorsally two pairs of eyes, and ventrally a pair of short two-jointed palps.
The Serpulidae are a family of sessile, tube-building annelid worms in the class Polychaeta. The members of this family differ from other sabellid tube worms in that they have a specialized operculum that blocks the entrance of their tubes when they withdraw into the tubes. In addition, serpulids secrete tubes of calcium carbonate. Serpulids are the most important biomineralizers among annelids. About 300 species in the family Serpulidae are known, all but one of which live in saline waters. The earliest serpulids are known from the Permian.
Spirobranchus is a small genus of tube-building annelid fanworms in the family Serpulidae.
Harmothoe is a genus of marine Polychaete worms belonging to the family Polynoidae. Species of Harmothoe are found world-wide to depths of at least 5,000 m but are more common in shallower water.
Janua is a genus of polychaetes, containing the following subgenera and species:
Oroperipatus is a genus of Neotropical velvet worms in the family Peripatidae.
Phyllodoce is a genus of polychaete worms, which contains about 200 species. The prostomium bears eyes, two pairs of antennae and a pair of large retractile nuchal organs. The eversible proboscis is clearly divided into two parts.
Eudistylia is a genus of marine polychaete worms. The type species is Eudistylia gigantea, now accepted as Eudistylia vancouveri. This worm lives in a parchment-like tube with a single opening from which a crown of tentacles projects when the worm is submerged. It is a sessile filter feeder. the Eudistylia Vancouveri is unique because it has an opiculum which makes it possible to fully retract into the tube when predators are sensed.
Amphinomidae, also known as the bristle worms or sea mice, are a family of marine polychaetes, many species of which bear chaetae mineralized with carbonate. The best-known amphinomids are the fireworms, which can cause great pain if their toxin-coated chaetae are touched or trodden on. Their relationship to other polychaete groups is somewhat poorly resolved.
Cirriformia is a genus of marine polychaete worms in the family Cirratulidae.
Protula is a genus of marine polychaete worms in the family Serpulidae.
Chloeia is a genus of marine polychaete worms.
Notocomplana is a genus of flatworms.
Eulalia is a genus of polychaete worms.
Bispira is a genus of marine bristleworm in the family Sabellidae. Its members were initially included in genus Sabella by Grube in 1851. In 1856, Krøyer described Bispira as a separate genus. Members of Bispira are defined by spirally-coiled, equally-divided branchial lobes.
Lepidonotus is a genus of marine annelids in the family Polynoidae. The genus occurs globally and includes 80 species, usually found in shallow waters down to about 80 metres.
Aglaophamus is a genus of free-burrowing nephtyid worms.
Hystricosoma is a genus of annelids belonging to the family Aeolosomatidae.
Hermodice is a genus of annelids belonging to the family Amphinomidae.
