The sphaerodorids are small, benthic polychaetes with series of epidermal protuberances in the form of tubercles or papillae covering the dorsum and usually also the ventrum. The prostomium and the peristomium are not clearly separated from each other or from the remainder of the body. The anterior end has three to seven prostomial antennae; a pair of peristomial cirri are usually present. The unarmed proboscis is eversible. The uniramous parapodia are usually equipped with single acicula. Setae may be composite or simple. A complete survey of all original descriptions with re-distribution of the species into the several genera is given in Appendix A. A diagnosis is given for each species seen by the present author.