20–37 segments; twelve pairs of elytrae, progressively increasing in length, followed by smaller foliaceous lamellae posteriorly; surface smooth. Anterior margin of first pair of elytrae with papillae or fimbriae; 0–10 papillae; lateral margins of elytrae 2–12 fimbriated; fimbriae entire; twelfth pair of elytrae with 17–24 marginal papillae. Branchiae number 11 pairs (on segments 8, 10, 12 ... 22, 23, 25, 26). Neuropodial ventral lamellae absent. Acicular neurochaetae present on anterior segments (on segment 3, or 3–4, only); dorsal neurochaetae of posterior segments strongly bent or curved ventrally.