Isabelia thomasii (Cookson and Eisenack, 1961) Lentin and Williams, 1976

Combination illegitimate since the generic name Isabelia is illegitimate.
Now Isabelidinium. Originally Deflandrea, subsequently Isabelia (combination illegitimate), thirdly (and now) Isabelidinium.

Holotype: Cookson and Eisenack, 1961, pl.11, fig.8
Paratype: Cookson and Eisenack, 1961
Locus typicus: Belfast No. 4 Bore, Victoria, Australia
Stratum typicum: Senonian

Original description: Cookson and Eisenacik, 1961, p.71-72: Deflandrea thomasii
Shell longer than broad, roughly oval with a median girdle with low borders which, sometimes, is only indicated at the lateral margins. The epitheca has a short, solid pointed horn which terminates in a minute hyaline prominance.
The antapex is variable in outline, it may be indented, obliquely truncate with a single short, pointed, lateral horn or broadly rounded. The shell membrane is 2 layered; the inner layer is thin and hyaline, the outer is formed of densely arranged minute granules or rods; it is from this layer that the apical horn is formed. In poorly preserved specimens the outer layer tends to be destroyed. The internal body is oval in outline and thin-walled; it appears to be absent from some specimens. The pylome is trapezoid in shape.
Dimensions: Type--length 108 Ám, breadth 82 Ám. Range--length 85-114 Ám, breadth 50-90 Ám.