Subgenus Monoplex G. Perry, 1811

Type species: Cymatium (Monoplex) parthenopeum parthenopeum (von Salis, 1793) Cymatium (Monoplex) parthenopeum echo Kuroda & Habe in Kira, 1961 Cymatium (Monoplex) parthenopeum keenae (Beu, 1970)
Cymatium parthenopeum parthenopeum Cymatium parthenopeum echo Cymatium parthenopeum keenae
Periostracum #1   Periostracum #2    
Type Species    
Cymatium (Monoplex) amictum (Reeve, 1844) Cymatium (Monoplex) aquatile (Reeve, 1844) Cymatium (Monoplex) corrugatum (Lamarck, 1816)
Cymatium amictum Cymatium aquatile  Cymatium corrugatum
   In Situ   In Situ #2   Living Animal  
Cymatium (Monoplex) gemmatum (Reeve, 1844) Cymatium (Monoplex) intermedium (Pease, 1869) Cymatium (Monoplex) krebsii (Mřrch, 1877)
Cymatium gemmatum Cymatium intermedium Cymatium krebsii 
Cymatium (Monoplex) macrodon (Valenciennes, 1832) Cymatium (Monoplex) mundum (Gould, 1849) Cymatium (Monoplex) nicobaricum (Röding, 1798)
 Cymatium macrodon Cymatium mundum Cymatium nicobaricum 
Cymatium (Monoplex) pileare (Linnaeus, 1758) Indo Pacific Cymatium (Monoplex) pileare (Linnaeus, 1758) Western Atlantic
Possible Cymatium nicobaricum Veliger Cymatium pileare (Indo Pacific) Cymatium pileare (Western Atlantic)
Cymatium (Monoplex) pileare (Linnaeus, 1758) Western Atlantic Cymatium (Monoplex) tranquebaricum (Lamarck, 1816) Cymatium (Monoplex) trigonum (Gmelin, 1791)
Cymatium pileare (Western Atlantic) Cymatium tranquebaricum Cymatium trigonum
Cymatium (Ranularia) turtoni (E. A. Smith, 1890)   Cymatium (Monoplex) vestitum (Hinds, 1844)
Cymatium turtoni   Cymatium vestitum