Parechinus miliaris Mortensen, 1903 – synonym of Psammechinus miliaris
Phyllophorus drummondii Forbes, 1841 – synonym of Thyonidium drummondii
Phyllophorus drummondii Thompson, 1840 – synonym of Thyonidium drummondii
Polypholis echinata Duncan, 18?? – synonym of Ophiopholis aculeata
Porania gibbosa Gray, 1840 – synonym of Porania pulvillus
Pseudocucumis cuenoti Koehler and Vaney, ???? – synonym of Neopentadactyla mixta
Pseudocucumis mixta Ostergren, 1898 – synonym of Neopentadactyla mixta
Psolinus brevis Forbes, 184?1 – synonym of Cucumaria frondosa
Psolus granulatus Ayres, 1851 – synonym of Psolus phantapus
Psolus laevigatus Ayres, 1851 – synonym of Psolus phantapus
Psolus regalis Verrill, 1866 – synonym of Psolus phantapus