Genus Bylgides Chamberlin, 1919

Type species. Bylgia elegans Théel, 1879

Diagnosis (after Pettibone 1993): Body with up to 38 segments. With up to 15 pairs of elytra on segments 2, 4, 5, 7; segments alternating up to segment 23, 26, 29, and 32; elytra with papillae, with or without microtubercles. Dorsal cirri on segments without elytra, with cylindrical cirrophores; dorsal tubercles nodular to digitiform on cirri bearing segments. Prostomium bilobed, with cephalic peaks more or less distinct, with three antennae, paired palps, and two pairs of eyes; median antenna with a ceratophore in the anterior notch; lateral antennae with ceratophores inserted ventrally. Tentaculophores of the first segment tentacular lateral to the prostomium, each with one aciculum, with or without chaetae, and dorsal and ventral tentacular cirri. Second segment or buccal segment with the first pair of elytra, biramous parapodia, and long ventral buccal cirri, laterally to the mouth; with or without a nuchal lobe; pharynx with nine pairs of marginal papillae and two pairs of hooks, shaped jaws. Biramous parapodia; welldeveloped notopodia and neuropodia; neuropodia with a conical pre-chaetal acicular lobe and digitiform supra-acicular process, post-chaetal lobe rounded. Notochaetae more robust than neurochaetae, with numerous rows of spines and short, smooth tips. Neurochaetae with elongated spiny regions, all with pointed tips or some with blunt acicular tips. Short ventral cirri on all segments. Pygidium with a pair of anal cirri.

Key to all species of Bylgides

1. Nuchal lobe present................................................................................... 2

Nuchal lobe absent................................................................................... 4

2(1). Presence of spots around the eyes, smooth notochaetae throughout.................... Bylgides samueli sp. nov. (Brazil)

Absence of spots around the eyes, spiny notochaetae throughout................................................ 3

3(2). Nodular dorsal tubercle............................................. Bylgides acutisetis Loshamn, 1981 (Norway)

Bulbous dorsal tubercle with a flattened digitiform process projecting laterally.................................................................................................... Bylgides annenkovae Pettibone, 1993 (Norway)

4(1). Elytra with microtubercles............................................................................. 5

Elytra without microtubercles........................................................................... 6

5(4). Neurochaetae with smooth capillary tips and some slightly hook-shaped tips, cylindrical elytral papillae with clavate tips and rounded chitinous bases.............................. Bylgides sarsi (variety) (Kinberg in Malmgren, 1866) (Sweden)

Neurochaetae with plumose and slender tips, clavate elytral papillae......... Bylgides macrolepidus (Moore, 1905) (Russia)

6(4). Presence of spots around the eyes; elytra smooth................................. Bylgides cinthyae sp. nov. (Brazil)

Absence of spots around the eyes; elytra papillated........................................................... 7

7(6). Filiform elytral papillae....................................... Bylgides fuscus (Hartman & Fauchald, 1971) (USA)

Elytral papillae otherwise............................................................................... 8

8(7). Indistinct nephridial papillae.......................................... Bylgides belfastensis Pettibone, 1993 (USA)

Distinct nephridial papillae............................................................................. 9

9(8). All neurochaetae with long capillary tips.................................................................. 10

Neurochaetae with capillary tips and some with slightly hook-shaped tips........................................ 11

10(9). Elytral papillae with circular base, tapering distally.................... Bylgides promamme (Malmgren, 1867) (Russia)

Elytral papillae with cylindrical base, not tapering distally............. Bylgides groenlandicus (Malmgren, 1867) (Russia)

11(9). Cylindrical elytral papilla with clavate tip and absent chitinous bases............. Bylgides elegans (Théel, 1879) (Russia)

Cylindrical elytral papilla without clavate tip and present chitinous bases.................................................................................................. Bylgides sarsi (Kinberg in Malmgren, 1866) (Sweden)