Slender, thread-like, cylindrical body with numerous similar segments. External segmentation poorly or not at all indicated. Parapodia and chaetae absent. Surface extremely smooth and somewhat iridescent; external ciliation lacking, except for the nuchal slits on the head, sometimes stiff sensory cilia on tentacles, and, exceptionally, scattered ciliary tufts. Prostomium with two short, stiff, laterofrontally directed tentacles that lack internal canals. Two pigmented eyes may or may not be present. Bulb-shaped pygidium with or without appendages, mostly pre-terminally encircled by groups of adhesive gland openings. Muscular pharyngeal bulb absent.
The following species of this genus occur in the region: