Baltisphaeridium malleoferum, (White, 1842), Downie and Sarjeant, 1965

Now Achomosphaera?. Originally Xanthidium (an extant desmid genus), subsequently Hystrichosphaeridium, thirdly Baltisphaeridium, fourthly (and now) Achomosphaera?. This combination was not validly published in Downie and Sarjeant, 1963 since these authors did not fully reference the basionym.

Holotype: White, 1842, pl.4, div.3, fig.7; Sarjeant, 1991, fig.4.6
Age: Late Cretaceous