Medium-sized to large; yellowish-white or grey, often with yellowish-brownish or dark brown pigments, never red. Head often small in relation to body length, mostly about 1.5x as long as wide; yellow to dark brown. Eye spots separate, dorsal eye-spot posterior to ventral eye spot.
With frontal apotome, weakly delimited clypeus and single or several labral sclerites.
Moderately long to relatively short, never reduced; 4 segmented; basal segment large; segments 3 and 4 small; segment 3 never annulate. Blade slightly shorter to slightly longer than flagellum. Lauterborn organs small but distinct, at apex of segment 2. Antennal segment 2 with well-developed style.
SI seta apically serrate, fringed or biarticulate with lateral fringe apically; SII and SIII simple, SIV normal or SIVA large and triarticulate. Labral lamellae either 2 broad pectinate lamellae or 2 setal tufts. Chaetae more or less serrate; 4-6 pairs; chaeta media often differentiated. Spinulae 3-4 or reduced to minute point. Pecten epipharyngis consisting either of free, subequal, scale-like spines, or of brushes of thin hair-like setae. With 5-7 pairs of simple or fringed chaetulae laterales; chaetulae basales usually 2 terminally notched or pointed pairs, sometimes very small. Premandible with 1 or 2 apical teeth; with or without brush.
With single apical tooth and 2-4 inner teeth. Pecten mandibularis absent, or brush-like. Seta subdentalis simple. Seta interna with 6-40 smooth or serrate branches.
With 13-15 teeth (up to 18 including accessory teeth); 1-2 median teeth. Ventromental plate large, extending far beyond outer mental tooth; with few to numerous and strong setae in ventromental beard, often in addition to cardinal beard.
Palp with about 9 tiny sensillae and 2 setae; sensillae distributed into 2 groups with bisensillum lying between the two. Galea with 6 sensillae, without pecten galearis. Laciniae low, with overlapping row of 6-8 chaetae. Cardinal beard present or absent.
Parapods well developed, separated, with apical claws; anterior parapods with serrate claws. Procercus about 2x as high as wide; with 2 strong lateral setae and 8 anal setae; spur absent. Anal tubules 2 pairs, shorter than posterior parapods. Body setae not conspicuous.