Baltisphaeridium piriferum, (Eisenack, 1954), Downie and Sarjeant, 1965

Now Visbysphaera (an acritarch genus). Originally Hystrichosphaeridium, subsequently Baltisphaeridium, thirdly Multiplicisphaeridium (an acritarch genus), fourthly (and now) Visbysphaera (an acritarch genus).
Tax. sr. synonym of the acritarch species Baltisphaeridium hermosum Cramer and Diez, 1968 (a name not validly published) according to Cramer, 1970. This combination was not validly published in Downie and Sarjeant, 1963 since these authors did not fully reference the basionym.

Holotype: Eisenack, 1954, pl.1, figs.1a-b
Age: Silurian (Late Llandovery)