From Fensome et al., 2019:
Tenua colliveri (Cookson and Eisenack, 1960b, p.251, pl.38, figs.3–4) Fensome et al., 2019a, p.47.
Holotype: Cookson and Eisenack, 1960b, pl.38, fig.4; Bint, 1986, text-fig.14E; Fensome et al., 2019a, fig.17T.
Originally Canningia, subsequently Circulodinium, thirdly Canninginopsis, fourthly (and now) Tenua Eisenack.
Age: Aptian.

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Original description as Canningia colliveri: [Cookson and Eisenack, 1960, p. 251]:

Description:
Shell with straight or rounded sides; apical projection not prominent, basal indentation clearly marked; a "girdle" is usually present slightly above the equator. Shell-membrane densely and irregular reticulate, the reticulum low, small-meshed and thick-walled.

Dimensions:
holotype - 107 µm long, 100 µm broad.
Paratype - 106 µm long, 90 µm broad.

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Supplemental description:

Mehrota and Sarjeant, 1987, p. 154:

Description:
Proximate cyst, cingulotabulate and lenticular, having a broad apical archaeopyle with a strongly zigzag margin. Antapex bilobate; the left lobe may bear a small horn (pl. 8, fig. 4).
Autophragm ornamented with granules that are isodiametric (less than 1 µm in diameter) and arranged in a regular manner. In addition the ornamentation sometimes also includes a few low spines (< 1 µm), distributed sparsely on the autoblast (pl. 8, fig. 4).
Cingulum suggested by flexures occupying the region of maximum cyst width. Sulcus not developed, though notch is developed.