« Shell nearly equivalve, subnacreous, with a more or less distinct tubercle in front of the resilium on the dorsal margin; ligament obsolete, cartilage internal with a large lithodesma; area obscure or none; beaks entire, valves almost closed; pallial sinus obsolete. » – W. H. Dall: “Contributions to the Tertiary fauna of Florida with especial reference to the Miocene silex-beds of Tampa and the Pliocene beds of the Caloosahatchie River”, Transactions of the Wagner Free Institute of Science vol.III part.3, Philadelphia 1895, p.533.
 

« Valves with radial and vertical undulations, gaping behind but not below… » – W. H. Dall: “Contributions to the Tertiary fauna of Florida with especial reference to the Miocene silex-beds of Tampa and the Pliocene beds of the Caloosahatchie River”, Transactions of the Wagner Free Institute of Science vol.III part.6, Philadelphia 1903, p.1514.