General features. Body shape vermiform; segments numerous (more than
about 15); regionation absent. Body opaque, gut usually not
visible. Pygidium simple ring or cone. Pygidial appendages present; one
pair of cirri, or one pair of cirri and single medial papilla.
Head & head structures. Head discrete and compact, dorsal to
mouth. Prostomium bluntly conical to trapezoidal (narrow end anteriorly).
Eyes present; one pair; situated on prostomium;
compound with lenses. Prostomial antennae present; paired arising
anterolaterally, or include paired anterolateral ones and single medial one;
smooth. Palps paired (resemble antennae); unarticulated; ventrolateral. Nuchal
organs indistinct paired dorsolateral patches, or paired posterior projections.
Peristomial ring absent.
Pharynx & pharyngeal apparatus. Foregut a muscular axial pharynx;
surface smooth, or with soft papillae; papillae irregularly arranged, or in
distinct rows; distal ring of papillae present.
Body segments & parapodia. First segment with tentacular cirri.
Tentacular cirri 2–4 pair(s); arise on a single segment, or over two or
more segments (segments often fused); internal aciculae absent. First chaetiger
with neurochaetae only. Parapodia uniramous
throughout; notopodial lobes absent; neuropodial lobes represented by at
least one chaetal lobe. Dorsal cirri flattened and
foliaceous. Ventral cirri present, cirriform or tapering, or foliaceous.
Branchiae absent.
Chaetae. Notochaetae absent, or present. Aciculae present; in ventral
position (=neuroaciculae). Capillary chaetae absent, or present; hair-like;
smooth. Spines absent. Hooks absent. Compound chaetae present;
appendage distally tapering to slender tips (=spinigerous);
appendage not canaliculated; appendage without hoods or guards;
joint distinctly asymmetrical (=heterogomph); joint effected by
ligament(s); shaft distinctly inflated distally near
joint; shaft without distinct core. Compound falcigers present in most
or all chaetigers.
Tube & burrow. Tube absent or unconsolidated. Burrow traces
absent.
