Deflandrea rectangularis Cookson and Eisenack, 1962

Now Amphidiadema. Originally Deflandrea, subsequently (and now) Amphidiadema.
Tax. jr. synonym of Hystrichosphaeropsis quasicribrata (O.Wetzel, 1961) Gocht, 1976, according to Stover and Evitt, 1978, who were following Gocht, 1976. Gocht, 1976, only considered the specimen of Amphidiadema rectangularis illustrated by Kjellstrom, 1973 (fig.17), to be synonymous.

Holotype: Cookson and Eisenack, 1962, pl.1, fig.14; Jan du Chêne et al., 1986, pl.48, figs.14-15
Locus typicus: Perth Basin, Australia
Stratum typicum: Late Turonian-Middle Senonian

Original description: Cookson and Eisenack, 1962, p.486
Shell elongate, flat, either nearly rectangular in outline or slightly narrowed above the limits of the capsule. Apex truncate to rounded, sometimes with a low central elevation. Antapex truncate to rounded or with slight indications of horns. Tabulation, girdle and longitudinal furrow absent. Capsule circular to oval in outline, generally reaching the lateral margins of the shell. Wall of shell and capsule smooth, that of the capsule being thinner.
Dimensions: Holotype: 120 Ám long, 60 Ám broad; capsule 40x58 Ám broad; pylome 24x26 Ám. Range: 100-130 Ám long, 56-64 Ám broad.