The Collaborative International Dictionary of English v.0.48:
Nereis \Ne"re*is\ (? or ?), prop. n.; pl. Nereides. [L.] 1. (Class. Myth.) A Nereid. See Nereid. [1913 Webster] 2. (Zool.) A genus, including numerous species, of marine chaetopod annelids, having a well-formed head, with two pairs of eyes, antennae, four pairs of tentacles, and a protrusile pharynx, armed with a pair of hooked jaws. [1913 Webster]