Nereididae Blainville, 1818

Prostomium with a narrow anterior and a wide posterior part (inverted T-shape) in most taxa; others with triangular or roughly diamond-shaped prostomia. Peristomium limited to lips. Paired frontal antennae present in almost all taxa. Palps ventral, tapering, articulated (but see Harper 1979: 95). Nuchal organs short ciliated grooves. Longitudinal muscles grouped in bundles; segmentation distinct. First segment indistinct with tentacular cirri only; four pairs of tentacular cirri present in most taxa; other taxa with two or three pairs. Both parapodial rami welldeveloped; notopodia shorter than neuropodia in most taxa. Dorsal and ventral cirri present. Gills and epidermal papillae absent. Paired pygidial cirri present. Lateral organs and dorsal cirrus organs not observed. Stomodaeum with axial, muscular eversible pharynx; terminal papillae absent; lateral jaws present. When everted outer surface of pharynx with either papillae or paragnaths or both in characteristic patterns in most taxa. Gular membrane absent; gut a straight tube. Metanephrida completely separated from ciliophagocytic organs; present in most segments. Circulatory system closed; heart body absent. Aciculae present. All chaetae compound; appendages joined to shafts by single ligaments. Appendages slender and tapering to fine tips, or bluntly falcate, sometimes dentate. (from Fauchald, K. & Rouse, G. W. (1997) Polychaete systematics: past and present. Zoologica Scripta, 26, 71-138.)

taxa with two or three pairs. Both parapodial rami welldeveloped;notopodia shorter than neuropodia in mosttaxa. Dorsal and ventral cirri present. Gills and epidermalpapillae absent. Paired pygidial cirri present. Lateralorgans and dorsal cirrus organs not observed. Stomodaeumwith axial, muscular eversible pharynx; terminalpapillae absent; lateral jaws present. When everted outersurface of pharynx with either papillae or paragnaths orboth in characteristic patterns in most taxa. Gularmembrane absent; gut a straight tube. Metanephridacompletely separated from ciliophagocytic organs; presentin most segments. Circulatory system closed; heart bodyabsent. Aciculae present. All chaetae compound; appendagesjoined to shafts by single ligaments (see below).Appendages slender and tapering to fine tips, or bluntlyfalcate, sometimes dentate.part (inverted T-shape) in most taxa; others with triangularor roughly diamond-shaped prostomia. Peristomiumlimited to lips. Paired frontal antennae present in almostall taxa. Palps ventral, tapering, articulated (but seeHarper 1979: 95). Nuchal organs short ciliated grooves.Longitudinal muscles grouped in bundles; segmentationdistinct. First segment indistinct with tentacular cirri only;four pairs of tentacular cirri present in most taxa; othertaxa with two or three pairs. Both parapodial rami welldeveloped;notopodia shorter than neuropodia in mosttaxa. Dorsal and ventral cirri present. Gills and epidermalpapillae absent. Paired pygidial cirri present. Lateralorgans and dorsal cirrus organs not observed. Stomodaeumwith axial, muscular eversible pharynx; terminalpapillae absent; lateral jaws present. When everted outersurface of pharynx with either papillae or paragnaths orboth in characteristic patterns in most taxa. Gularmembrane absent; gut a straight tube. Metanephridacompletely separated from ciliophagocytic organs; presentin most segments. Circulatory system closed; heart bodyabsent. Aciculae present. All chaetae compound; appendagesjoined to shafts by single ligaments (see below).Appendages slender and tapering to fine tips, or bluntlyfalcate, sometimes dentate.