recurvatum (White, 1842, p.39, pl.4, fig.12) Lejeune-Carpentier, 1940, p.B221–B222. Holotype: White, 1842, pl.4, fig.12. Originally Xanthidium tubiferum var. recurvatum (Appendix A), subsequently (and now) Hystrichosphaeridium recurvatum. Nomenclatural junior synonyms: Xanthidium tubiferum var. palmatum [subsequently Hystrichosphaeridium palmatum (White), an illegitimate name], Xanthidium tubiferum var. palmaforme and Hystrichosphaeridium duplum, since they all have the same holotype as Hystrichosphaeridium recurvatum. White (1842, p.39) named "The twelfth ... species of the genus Xanthidium ... the Tubiferum recurvatum or palmaforme — the curved or palm-formed Tubiferum", thus presenting two epithets in his text. To compound matters, the single illustration was labelled "X. tubiferum palmatum". Since prior to 1953 alternative names were allowed under the I.C.N., and since White (1842) provided a description and illustration, the taxon was validly published. The correct name would be that chosen by the first subsequent author to make such a choice, and this was Bronn (1848, p.1375), who used the name Xanthidium palmatum, at species rank. When Downie and Sarjeant (1965, p.121) transferred Xanthidium palmatum to Hystrichosphaeridium, they created an illegitimate combination — a junior homonym of Hystrichosphaeridium palmatum Deflandre and Courteville. Hence, since Xanthidium tubiferum var. recurvatum had been raised to specific rank, as Hystrichosphaeridium recurvatum, by Lejeune-Carpentier (1940), "recurvatum" becomes the correct epithet as long as the epithet "palmatum" remains unavailable. Age: Late Cretaceous.