Gonyaulacysta margaritifera (Cookson and Eisenack, 1960) Sarjeant, 1966

Now Impagidinium. Originally Gonyaulax, subsequently Gonyaulacysta (combination not validly published), thirdly Leptodinium, fourthly (and now) Impagidinium.
Combination not validly published since Sarjeant, 1966, did not fully reference the basionym.
Holotype: Cokson and Eisenack, 1960, pl.2, fig.1; Jan du Chêne at al., 1986, pl.54, fig.6
Locus typicus: Carnarvon Basin, Western Australia
Stratum typicum: Campanian

Original description: Cookson and Eisenack, 1960, p.5: Gonyaulax margaritifera
Shell small, sphaerical to slightly oval, equally divided by a distinct helicoidal girdle, epitheca and hypotheca without distinct projractions. Plates bordered by ledges, which are perforated by a single row of holes, the perforations of the wall between the holes being so thickened that in surface view the ledges appear like strings of beads. Sometimes, in small localized areas, the ledges are higher than normal and form loop-like tufts.
Dimensions: Holotype: 52 µm long, 49 µm broad. Range 43-52x42x49 µm.