The capitellid genus Notodasus Fauchald, 1972 is emended and its previously known species are redescribed. Since the original descriptions of N. magnus Fauchald, 1972, N. dexterae Fauchald, 1973, and N. arenicola Hartmann-Schröder, 1992 omitted important morphological details and were either incomplete or misleading, these species are redescribed based upon examination of type materials. Four new species are described from tropical localities in Mexico: Notodasus harrisae n. sp., N. hartmanae n. sp., N. kristiani n. sp. and N. salazari n. sp. Standardised descriptions are provided for all species including the methyl green staining pattern, the epithelial texture and the shape of hooded hooks. A key for all described species is provided.