Trithyrodinium velatum (Conrad, 1941, p.8–9, pl.1, fig.A ex Sarjeant, 1967b, p.256) Riding and Fensome, 2003, p.24.

Originally Palaeoperidinium (name not validly published), subsequently Scriniodinium?, thirdly Palaeoperidinium? (combination not validly published), fourthly (and now) Trithyrodinium?. Questionable assignment: Riding and Fensome (2003, p.24).
The name Palaeoperidinium velatum was not validly published in Conrad (1941) since the generic name Palaeoperidinium was not validly published until 1967. Williams et al. (1998, p.550) accepted Sarjeant's (1967b) indirect reference to Conrad (1941) as indication of a type (I.C.N. Article 40.3).

Holotype: Conrad, 1941, pl.1, fig.A.
Age: Maastrichtian.