Body square-built and relatively broad.
Prostomium semicircular without eyes. Prostomium with 3 antennae and 2 simple palps. Lateral antennae and palps of same size, with smooth edges without hairs. Median antenna clearly longer than lateral ones and inserted at the level of the first ventral tentacular cirri.
3 pairs of simple tentacular cirri on 2 segments.
Dorsal tentacular cirri of first segment as long as median antenna. Tentacular cirri of second segment clearly the longest. Parapodia subbiramous. Dorsal and ventral cirri thread-like and simple. Dorsal cirri short at maximum one fourth of palp length and length of lateral antennae. Ventral cirri even shorter.
Notopodia with 1 acicula and 2-4 simple chaetae. Neuropodia with 2 aciculae and several compound chaetae (H. maxima-detail).
Pygidium with 2 thread-like cirri and pygidial plate, incised in the middle of the posterior edge, more or less bilobed. Pharynx with 10 terminal papillae, without jaws.
Body up to 5 mm for 16 or more segments.
Anterior and posterior parapodia transparent, rest of body dim milky. Dorsally with reddish-brown granulae. Additional with red or red-brown spot on the basis of dorsal tentacular cirri of the first segment.
Eastern Atlantic, Mediterranean, North Sea.