From Fensome et al., 2019:
Amphidiadema rectangularis ssp. samuelsonii, (Kjellström, 1973, p.22, fig.18) Lentin and Williams, 1976, p.61.
Holotype: Kjellström, 1973, fig.18.
Originally Deflandrea rectangularis var. samuelsonii, subsequently Deflandrea rectangularis subsp. samuelsonii, thirdly Amphidiadema rectangularis subsp. samuelsonii.
Taxonomic senior synonym: Triblastula (now Hystrichosphaeropsis) quasicribrata, according to Gocht (1976, p.322).
Age: early–late Maastrichtian.

Locus typicus: Höllviken Borehole No. 1, Scania, Sweden

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Original description as Deflandrea rectangularis ssp. samuelsonii: [Kjellström, 1973, p. 22]:

Diagnosis:
A variety of Deflandrea rectangularis with rectangular, granular theca. Spherical, psilate inner capsule extending to the lateral margins of the central part of the theca.
Archaeopyle intercalary.

Dimensions:
Length of theca: 140 µm; diameter of central capsule: 60 µm

Affinities:
This variety differs from D. rectangularis by having a granular theca wall and a psilate central capsule.