Arwidsson 1907; Day 1967; Fauchald 1977.
Type species: Sabella lumbricalis Fabricius, 1780, by monotypy.
Emended diagnosis: Head without cephalic shield; anal plate with well-developed edge dorsally and ventrally; nuchal grooves straight and parallel, curved, or divergent; all rostral uncini in single row; acicular spines on setigers 1–3, rarely on 1–4; anal funnel with distal margin in lateral view straight, or slightly truncate obliquely; anal plate with unequal anal cirri.
Remarks. Arwidsson (1907) reorganized the genus Nicomache into two subgenera on the basis of the shape of the anal funnel in lateral view. Nicomache (Nicomache) is characterized by having a straight, nonoblique distal margin in lateral view, while Nicomache (Loxochona) is diagnosed as having a distally obliquely truncate anal funnel in lateral view. Imajima & Shiraki (1982) describe some species of this genus, which confirm this classification scheme. Another important diagnostic character refers to edge of the anal plate. This edge is well developed both dorsally and ventrally in Nicomache. In Petaloproctus Quatrefages, 1865 only the ventral edge is well developed, while the dorsal edge is reduced (Arwidsson 1907; Imajima & Shiraki 1982).