(Figs. 3, 13A–I)
Polynoe clavigera M. Sars, 1863: 294.
Harmothoe impar pagenstecheri Michaelsen, 1896: 7, pl. 1 fig. 1 [new synonymy].
Harmothoe impar: Fauvel (1923): 59, fig. 21a–f [part]; Tebble & Chambers (1982): 40, figs. 7b, 12b–c, 38 [part]; Hartmann-Schröder (1996): 48, fig. 13 [part].
Harmothoe pagenstecheri: Chambers & Muir (1997): 108, fig. 28; Barnich & Fiege (2000): 1909, fig. 10A–D; Barnich & Fiege (2003): 52, fig. 26A–D.
Type material. Polynoe clavigera: holotype, ZMO C3225, Norway, Christiansund, 30–40 fms. Harmothoe impar pagenstecheri: holotype, ZMH V1081, North Sea, Helgoland, leg. Pagenstecher.
Additional material. NE Atlantic:1 spm., SMF 12428, France, Presqu'île de Quibéron, Pointe du Congruel, intertidal, under stones, 08 April 1997, leg. C. d’Udekem d’Acoz. 1 spm., SMF 17275, France, Roscoff, between Lithothamnium, August 2005, leg. T. Wehe.
(For further material see Barnich & Fiege 2000 and 2003).
Diagnosis. Anterior pair of eyes dorsolateral at widest part of prostomium. Elytral margin with fringing papillae; surface covered by conical microtubercles and few scattered papillae, with a row of large clubshaped, distally papillate macrotubercles near posterior margin.
Description (based on holotype of P. clavigera).
Body with 38 segments. At anterior end (Fig. 13A), prostomium bilobed, with distinct cephalic peaks; ceratophore of median antenna in anterior notch, lateral antennae inserted ventrally, styles of antennae papillate, slightly inflated subdistally, then abruptly tapering; anterior pair of eyes situated dorsolaterally at widest part of prostomium, posterior pair dorsally near hind margin of prostomium; palps papillate, tapering.
Tentaculophores inserted laterally to prostomium, each with one or two notochaetae and a dorsal and ventral tentacular cirrus, styles of cirri papillate, slightly inflated subdistally, then abruptly tapering. Second segment with first pair of elytra, biramous parapodia, and long buccal cirri. Following segments with tapering, short ventral cirri.
Fifteen pairs of elytra, covering dorsum, on segments 2, 4, 5, 7, then on every second segment to 23, 26, 29, 32; last six segments cirrigerous; elytral margin with fringing papillae; surface covered by conical microtubercles and few scattered papillae, with a row of large club-shaped, distally papillate macrotubercles near posterior margin; some elytra with additional extra-large spiny macrotubercle near posterior margin (Fig. 13B–D). Cirrigerous segments with distinct dorsal tubercles; dorsal cirri with cylindrical cirrophore, style papillate, slightly inflated subdistally, then abruptly tapering.
Parapodia biramous; notopodia with elongate acicular lobe; neuropodia with elongate prechaetal acicular lobe with digitiform supra-acicular process; neuropodial postchaetal lobe shorter than prechaetal lobe, rounded; tips of noto- and neuroacicula penetrating epidermis (Fig. 13E). Notochaetae stouter than neurochaetae, with distinct rows of spines and blunt tip (Fig. 13F); neurochaetae with distinct rows of spines, mostly bidentate with secondary tooth, some upper and lower unidentate (Fig. 13G–I).
Measurements. P. clavigera, holotype, ZMO C3225: L 28 mm, W 8 mm for 38 segments. H. impar pagenstecheri, holotype, ZMH V1081: L 21 mm, W 7 mm for 35 segments (last segments missing).
Remarks. The comparison with the type material of P.clavigera leaves no doubt that H. pagenstecheri is a junior synonym of H. clavigera.
Distribution. Northeast Atlantic, North Sea, Channel, and Mediterranean Sea.
Habitat. Between Posidonia rhizomes and algae, littoral down to 60 m.