Redescriptions of Lepidasthenia elegans, L. digueti, and Lepidametria commensalis (Polychaeta: Polynoidae)

To clarify the differences between Lepidasthenia Malmgren, 1867 and Lepidametria Webster, 1879, specimens of their type species are redescribed and illustrated. Diagnoses for both genera, a key to species of Lepidasthenia with giant neurochaetae, and a key to species of Lepidametria are included. Lepidasthenia elegans (Grube, 1840), described from the Gulf of Naples, has blocks of black segments alternating with a pale segment, posterior elytrigerous segments blackish; median and posterior segments with elytra every third segment; parapodia without notochaetae; neuropodia with neuropodial pre- and postchaetal lobes with margin entire; median segments with upper single neurochaetae thin, 1-2 giant neurochaetae barely denticulate, and medium-width neurochaetae with tips unidentate (accessory denticle minute). Lepidasthenia digueti Gravier, 1905, described from the Gulf of California living with balanoglossid hemichordates, is redescribed and reinstated. Lepidametria commensalis Webster, 1879, described living with terebellid polychaetes in Virginia, USA, has a brownish transverse segmental band along body; median segments with elytra alternating with dorsal cirri, posterior segments with series of 3-4 elytrigerous interrupted by 1 cirrigerous segment; parapodia with notochaetae; neuropodia elongate with neuropodial prechaetal lobe with upper area lobate, lower one entire, post-chaetal lobe entire; neurochaetae bidentate, median segments with giant neurochaetae barely denticulate.