Baltisphaeridium geometricum, (Pastiels, 1948 ex Downie and Sarjeant, 1965), Fensome et al., 1990

NOW Apectodinium. Originally Hystrichosphaeridium geometricum (name illegitimate), subsequently Baltisphaeridium geometricum, thirdly Apectodinium pastielsii (name illegitimate), fourthly (and now) Apectodinium pastielsii.
Nomenclatural junior synonym: Apectodinium pastielsii, which has the same type.
Taxonomic junior synonym (at specific rank): Wetzeliella homomorpha var. quinquelata (as Wetzeliella quinquelata; now Apectodinium quinquelatum), by implication in Harland (1979c, p.67), who believed the latter to be the senior name — however, Lentin and Williams (1989, p.18) retained Apectodinium quinquelatum.

Holotype: Pastiels, 1948, pl.4, fig.4
Age: Early Eocene (Ypresian)