Taxonomy of the Cambrian trilobite family Nepeidae is revised. Morphometric analyses of the genera 'Nepea' and 'Penarosa' demonstrate that use of proportions of linear dimensions of the cranidium to differentiate species is invalid, and that infrageneric variation is continuous. The taxonomy and biostratigraphy of all Australian species of Nepeidae is revised. Species considered valid herein include: 'Nepea narinosa' (type species), 'N. tonsillata', 'N. nans', 'Penarosa retifera' (type species), 'P. elaticeps', 'P. rhinodelphis', 'P. netenta', 'Loxonepea loxophrys' (type species) and Ferenepea hispida (type species). Folliceps is considered to be a junior subjective synonym of 'Nepea', 'Trinepea' is regarded as a junior subjective synonym of 'Penarosa', and Ascionepea is considered to be a junior subjective synonym of Ferenepea.