Two insufficiently described marine euplotids, Diophrys irmgard Mansfeld (1923) and Diophrys hystrix Buddenbrock (1920), found in coastal waters near Qingdao, China, were reinvestigated with emphasis on their living morphology and infraciliature. Improved diagnoses and redescriptions are supplied for both organisms. Critical redefinitions of nine morphotypes are presented and the validities of the nominal species are discussed and briefly revised. Following Curds and Wu (1983), and based on data obtained during the present study and a critical review of the literature, five additional nominal species are regarded as junior synonyms of known forms: Diophrys quadricaudatus Agamaliev (1967), D. scutoides Agamaliev (1967), and D. tetramacronucleata Kattar (1970) are synonymized with D. scutum (Dujardin 1841), while D. pentacirratus Alekperov (1984) and D. multicirratus Alekperov (1984) are junior synonyms of D. oligothrix Borror (1965).