Moore, 1910
Description:
A scale-worm with a body of uniform width. Dorsal and ventral surfaces smooth.
Prostomium bilobed, with a peak on each lobe, a papillated median antenna, a pair of lateral antennae, ventrally inserted, and a pair of palps. Two pairs of eyes, the anterior pair on the line of greatest width, the posterior pair near the rear margin.
First segment bearing chaetae and a pair of dorsal and ventral tentacular cirri. Scales overlap, covering the body. The first pair of scales are round, the rest oval to kidney-shaped, a quarter to a half of the margins fringed with small papillae, the surfaces covered with small tubercles and with a row of flattened discs extending over the posterior border. Notopodia are small mounds with a ventral acicular ligule and abundant chaetae. Notopodial chaetae spinose with blunt tips.
Neuropodia well developed with an anterior ligule and chaetae. Neuropodial chaetae of 2 kinds: 1) spinose along most of the length with unidentate tips; 2) spinose on the terminal quarter and with bidentate tips (H. fragilis-detail).
Size:
Up to 26 mm for 41 chaetigers.
Colour:
Dorsal surface brown with two transverse white lines per segment.
Habitat:
Sublittoral to 2900 m, on fine sand.
Distribution:
Arctic, North Pacific, North Atlantic up to English Channel, Skagerrak, Kattegat, Öresund.