From Williams et al., 2017:

[Actiniscus, (Ehrenberg, 1841, p.149–150), Ehrenberg, 1843a, p.103.
Siliceous dinoflagellate genus.

Originally Dictyocha subgenus Actiniscus, subsequently (and now) Actiniscus.
Tax. jr. syn.: Lutetianella (name not validly published) and Microdistephanus (name not validly published), both according to Dumitrică (1973, p.820); Gymnaster, according to Dumitrică (1973, p.820).
The designation of Actiniscus pentasterius as "type species" by Downie and Sarjeant (January, 1965, p.81–82) has precedence over the designation of Actiniscus elegans as "type species" by Norris and Sarjeant (March, 1965, p.9). Dumitrică (1973, p.820) considered the extant genus Diaster Meunier, 1909 to be a possible taxonomic junior synonym of Actiniscus. The name Actiniscus was first used in Ehrenberg (1841), who cited the name twice as as sub-entity of Dictyocha — "Dictyocha (Actiniscus) Pentasterias" (p.149) and "Dictyocha (Actiniscus) Sirius" (p.150). It was next mentioned by Ehrenberg (1843a, p.103) as "Actiniscus Sol und septenarius" within non-descriptive text. It is not clear to us that the generic name
Actiniscus should be considered validly published by Ehrenberg (1841, 1843a) as it lacks a description in those publications. But for now we follow the general concensus in accepting the name as valid as of 1841 as a subgenus, raised to generic rank in Ehrenberg (1843a).

Type species: not designated; "type species" is Actiniscus pentasterias, designated by Downie and Sarjeant (January, 1965, p.81–82)]