Cordosphaeridium microtriainum (Klumpp, 1953) Eisenack 1963

Now Operculodinium. Originally Hystrichosphaeridium, subsequently Cordosphaeridium, thirdly Polysphaeridium, fourthly Achomosphaera, fifthly (and now) Operculodinium.
Stover and Evitt, 1978, considered this to be a problematical species of Cordosphaeridium. Kar, 1979, transferred this species to Polysphaeridium Davey and Williams, 1966. Lentin and Williams, 1981, retained it in Cordosphaeridium.
Holotype: Klumpp, 1953, pl.17, fig.6-7; Sarjeant, 1981, pl.2, fig.1-2, text-fig.2
Paratypes: Klumpp, 1953
Locus typicus: Woehrden, Holstein, Germany
Stratum typicum: Late Eocene
Translation Klumpp, 1953: LPP

Original description: Klumpp, 1953, p. 390: Hystrichosphaeridium microtriaina
Diagnosis: A species of the genus Hystrichosphaeridium with the following special characteristics: the membrane of the shell is bi-layered. The numerous processes are formed by the outer layer and terminate in three small hooks.
Description: The shell appears relatively delicate, the outer layer is irregularly sculptured, the netlike ridges rising along the hollow processes.
Diameter: 48 µm; process length: 24-26 µm.
Variation: Diameter 44-100 µm, processes12-36 µm.