From Fensome et al., 2019:
Endoscrinium galeritum ssp. fornicatum (Klement, 1960, p.25–26, pl.1, figs.7–12) Lentin and Williams, 1973, p.54. Holotype:
Klement, 1960, pl.1, figs.7–8; Jan du Chêne et al., 1986a, pl.107, figs.4–6; Fensome et al., 1995, figs.1–2 — p.1489. Originally Scriniodinium galeritum subsp. fornicatum, subsequently (and now) Endoscrinium galeritum subsp. fornicatum. Age: middle Oxfordian.

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Original diagnosis: Klement, 1960, p.25: Scriniodinium galritum ssp. fornicatum
A subspecies of Scriniodinium (endoscrinium) galeritum, characterized by apical, antapical and marginal thickened bulge of the outer shell. It is marginally not flattened. Spiral girdle furrow, slighly indented, of medium breadth. Offset of the ends about two girdle widths. Plates convexly vaulted; sutures thickened lash-shaped.
Dimensions: Holotype: outer shell 89:75 µm, inner body 66:63 µm

Affinities: Klement, 1960, p. 26: Scriniodinium galritum ssp. fornicatum
The thickened bulges of the external membrane are a good distinctive criterium to the related subspecies S. galeritum galeritum.