provided by World Register of Marine Species
Small, cylindrical, grub-shaped animals. Prostomium, peristomium, species-specific number of segments, first and various number of posterior segments without chaetae. Palps, antennae, parapodia and pygidial cirri absent. Chaetae more or less simple arranged in paired ventrolateral bundles. Epidermis without locomotory cilia, whitish transparent, body surface slightly iridescent, eyes absent, nuchal organs either internalized or absent. Alimentary canal comprises a ventral pharynx with a large glandular complex, oesophagus, stomach and coiled intestine. Coelom, at least 2 pairs of metanephridia, blood vascular system and heart body present. Gonochoristic, gonoducts present, direct development (Westheide, 2008).