From Fensome et al., 2019:
Trithyrodinium striatum Benson, 1976, p.197–198, pl.11, figs.4–8.
Holotype: Benson, 1976, pl.11, figs.4–6.

Locus typicus: Round Bay, Maryland
Stratum typicum: Late Maastrichtian

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Original diagnosis: Benson, 1976, p.197
Cavate cyst with very thin, delicate periblast, which is frequently missing. Apical horn short, antapical horns unequally developed. Tabulation absent. Archeopyle intercalary, type 3I/3I. Periphragm thin, less than 0.5 Ám thick with no distinct sculpture, endophragm about 1 Ám thick, longitudinally striate with clear indication of cingulum.
Dimensions: Holotype: Periblast length 82 Ám; width 73 Ám endoblast length 65 Ám; width 62 Ám, apical pericoel 8 Ám.