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

Now Exochosphaeridium?. Originally Xanthidium (an extant desmid genus), subsequently Hystrichosphaeridium, thirdly Baltisphaeridium, fourthly
Exochosphaeridium, fifthly (and now) Exochosphaeridium?; see also Cordosphaeridium (combination not validly published).
Sr. homonym of Baltisphaeridium spinosum Rasul, 1979. 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, fig.6
Age: Late Cretaceous