From Williams, Lentin and Fensome 1998 - Lentin and Williams Index of Fossil Dinoflagellates:

[Achomosphaera ramulifera ssp. perforata, (Davey and Williams, 1966a, p. 50, pl.5, figs.1,4), Lentin and Williams, 1973, p. 10.

Holotype: Davey and Williams, 1966a, pl.5, fig.4; Bujak et al., 1980, pl.5, fig.1; Fensome et al., 1991, fig.2 - p.705; fig.3 - p.721.]
Locus typicus: London Clay, Isle of Wight, England
Age: Early Eocene

-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original diagnosis: [Davey and Williams, 1966, p. 50]:

Diagnosis:
A variety of A. ramulifera with gonal processes fenestrate proximally and sometimes distally.

Dimensions:
holotype: diameter of central body 33 by 42 µm, length of processes 16-18 µm.
Range: diameter of central body 33-56 µm, length of processes 15-26 µm.

Affinities:
The forms placed in A. ramulifera var. perforata differ from the typical A. ramulifera by the presence of perforate processes. This characteristic was not thought distinctive enough to justify the creation of a new species.