From Fensome et al., 2019:

Neonorthidium, Marheinecke, 1992, p.117.
Taxonomic junior synonym: Northidium (name not validly published), according to Marheinecke (1992, p.117). Contrary to the opinion of Lentin and Williams (1993, p.447), Williams et al. (1998, p.421) considered Neonorthidium to be validly published.
Type: Marheinecke, 1992, pl.26, figs.12–14; text-fig.23, as Neonorthidium perforatum.

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Original description: [Marheinecke, 1992]: (Translation: LPP):

Diagnosis:
Two-layered, cavate dinoflagellate cyst. Endoblast sphaeroidal to ovoidal. Wall thick, smooth or with low ornamentation, usually granulate. Periblast sphaeroidal to ovoidal divided into regular areas by sharp folds. Wall thin, clearly separated from endoblast. Contact between both at archaeopyle, ventral and dorsal. The periblast can be slightly granulate or smooth, perforate or nonperforate. The ornamentation can differ from area to area on single specimen.
Archaeopyle: apical, according to apicalsutur 1`+2`+3`+4`, operculum secate, ?foederate.
Areation: Indicated by archaeopyle and maybe by areation of the periblast.

Affinities:
In difference to Leberocysta is the periblast of Neonorthidium regularly areate and of constant form.