The taxonomic relationships of some Australian species of the agnostid subfamily Ptychagnostinae are discussed and some revisions made. The genus Ptychagnostus consists of two species, P. punctuosus and P. affinis. Zeteagnostus is emended to include Z. incautus and Z. scarifatus. Acidusus is emended to include A. atavus, A. acidusus, A. germanus, A. occultatus, A. michaeli, A. aculeatus and tentatively A. cassis. Onymagnostus includes O. hybridus, O. mundus and O. semiermis. Pentagnostus is monospecific, consisting of P. praecurrens. Triplagnostus is subdivided into two subgenera: T.(Triplagnostus) containing T.(T.) gibbus, T.(T.) scopus and T.(T.) ultimus; and T.(Aotagnostus) containing T.(A.) culminosus, T.(A.) aotus and T.(A.) magniceps.
- Middle cambrian