The data on the genus Peronopsis, including 116 species and subspecies, that is, at least half of Middle Cambrian agnostians, are completely revised. The revision is based on the order of the formation of pygidial characters in ontogeny. A convenient taxonomic system of abundant species of this genus is proposed. It is shown that the sequence of the formation of characters in ontogeny generally corresponds to the chronological sequence of the appearance of species with appropriate morphology. The study of the genus Peronopsis resulted in a revision of the species composition of some other genera of the family Peronopsidae, clarification of the periods of existence of the majority of genera of this family. New diagnoses of genera and subgenera of the family Peronopsidae are provided.
