Hystrichosphaeridium hirsutoides var. hamatum

"var. hamatum" Downie, 1958, p.335, pl.16, fig.1; text-figs.2j–k.  Holotype: Downie, 1958, pl.16, fig.1.  NOW Baltisphaeridium hamatum (Appendix A).  Originally Hystrichosphaeridium hirsutoides var. hamatum, subsequently Baltisphaeridium hirsutoides var. hamatum (Appendix A), thirdly Micrhystridium hamatum (Appendix A), fourthly Acanthodiacrodium hamatum (Appendix A), fifthly (and now) Baltisphaeridium hamatum (Appendix A).  Age: Early Ordovician.

Parent: Hystrichosphaeridium hirsutoides