A new species of Nicon Kinberg, 1866 (Polychaeta, Nereididae) from Ecuador, Eastern Pacific, with a key to all known species of the genus Author Leon-Gonzalez, Jesus Angel de Author Trovant, Berenice text ZooKeys 2013 269 67 76 http://dx.doi.org/10.3897/zookeys.269.4003 journal article http://dx.doi.org/10.3897/zookeys.269.4003 1313-2970-269-67 Nicon Kinberg, 1866 emended Type species. Nicon maculata Kinberg, 1866. Diagnosis. Prostomium pyriform to subpyriform, with two pairs of eyespots, paired frontal antennae and biarticulate palps. Four pairs of tentacular cirri with distinct cirrophores, smooth or articulated. Parapodia of first two chaetigers subbiramous, notopodium represented by a single ligule with dorsal cirri at its base. Subsequent notopodia with dorsal and ventral ligules with or without a small notopodial prechaetal lobe decreasing in far posterior parapodia. Neuropodia with superior and inferior prechaetal lobes, digitiform or conical postchaetal lobe present or absent along body, and a ventral ligule which can be reduced in posterior parapodia; ventral cirri short, tapered. All notochaetae homogomph spinigers; neurochaetae homogomph, heterogomph or sesquigomph falcigers, may be accompanied by homogomph and heterogomph spinigers, and simple chaetae. Pygidium with paired anal cirri. Pharynx with paired mandibles, without paragnaths or papillae. Remarks . This generic diagnosis was modified from Pettibone (1971) , Wu and Sun (1979) and Hutchings and Reid (1990) . Some important characteristics were not included by Pettibone (1971) because at that time she recognized Nicon maculata as the only member of the genus. Later on, Wu and Sun (1979) and Hutchings and Reid (1990) expanded the genus diagnosis including characters of recently described species such as Nicon japonicus Imajima, 1972, Nicon yaguinae Fauchald, 1972, Nicon sinica Wu & Sun, 1979 and Nicon rotunda Hutchings & Reid, 1990. Some new characters included in the present diagnosis are the presence-absence of a notopodial prechaetal lobe, and the occurrence of neuropodial sesquigomph falcigers.