From Fensome et al., 2019:
Trigonopyxis Cookson and Eisenack, 1960a, p.11. Name illegitimate -- senior homonym: Trigonopyxis Penard, 1912. Substitute name: Trigonopyxidia. Type: Cookson and Eisenack, 1960a, pl.3, fig.19, as Trigonopyxis ginella.

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Original description: [Cookson and Eisenack, 1960]:

Description:
Shell flat, triangular in outline, partially filled with a capsule.