Gonyaulacysta apionis (Cookson and Eisenack, 1958) Sarjeant, 1969

NOW Cribroperidinium. Originally Gonyaulax, subsequently Gonyaulacysta, thirdly Millioudodinium, fourthly (and now) Cribroperidinium.
Tax. jr. synonym of Gonyaulax (now Cribroperidinium) edwardsii Cookson and Eisenack, 1958 (Davey, 1969), according to Burger, 1980, Yun, 1981, And Lentin and Williams, 1985. Jan du Chêne et al., 1986, retained Gonyaulacysta (as Cribroperidinium) apione as a separate species.
This combination was not validly published in Sarjeant, 1966, since that author did not fully reference the basionym.
Holotype: Cookson and Eisenack, 1958, text-figs.3-4; Jan du Chêne et al., 1986, pl.33, fig.6
Paratype: Cookson and Eisenack, 1958
Locus typicus: Cootabarlow, S Australia
Stratum typicum: Albian

Original description: Cookson and Eisenack, 1958, p. 36: Gonyaulax apionis
Shell smooth nearly twice as long as broad, epitheca long, conical, sumounted by a long, stiff horn which is closed at one end by a "lid" with a short central projection. The girdle is strongly helicoid and bordered by low but rather sharp ledges. The hypotheca is more dome-shaped and the antapical plate is square with four small pointed projections at the corners. The ledges borgering the plate are smooth and low. In the type a long narrow pylome straches from the base of the horn to the girdle (plate 3""). The tabulation, though rather distinct, cannot be given in full detail; it appears to be simple.
Dimensions: Type 105x57 µm, horn 20 µm. A paratype 114-71 µm, horn 24 µm.

Affinities:
Cookson and Eisenack, 1958, p. 36: Gonyaulax apionis
The long narrow shape, smooth surface and absence of ornamentation distinguish G. apionis from all other known fossil species of Gonyaualx.