Pseudopleonexes sheardi n.sp. is reported from South Australia. This is the second named species in the genus known previously only from New Zealand. Conlans (1982) original diagnosis of the genus (type species Pleonexes lessoniae Hurley, 1954) and the diagnosis in Barnard & Karaman (1991) differ in several respects. Thirty-six characters from those diagnoses and from Pseudopleonexes sheardi are compared in a table, and a number of those characters are discussed. Pseudopleonexes sheardi differs from Conlans diagnosis in the palm of gnathopod 1 being slightly oblique rather than transverse, and in the reduced palp of maxilla 1 having a single article rather than 2. In view of several synapomorphies identified, those differences do not warrant separate generic recognition of P. sheardi. A new diagnosis of Pseudopleonexes is given. Specimens from New Zealand referred to P. lessoniae by Barnard (1972, as Ampithoe (Pleonexes) lessoniae) are discussed. The specimens probably represent two separate species, neither belonging to P. lessoniae. Further material is required to confirm or reject their inclusion in Pseudopleonexes.