Xanthidium tubiferum Ehrenberg, 1837b, pl.1, fig.16. Emendation: Davey and Williams, 1966b, p.56–58, as Hystrichosphaeridium tubiferum.

NOW Hystrichosphaeridium tubiferum. Originally Xanthidium tubiferum, subsequently Hystrichosphaera tubifera (combination not validly published), thirdly (and now) Hystrichosphaeridium tubiferum, fourthly Ovum hispidum subsp. tubiferum (combination not validly published; Appendix A).
Taxonomic junior synonym: Xanthidium (as Hystrichokolpoma) bulbosum, according to Stover and Evitt (1978, p.55) — however, Lentin and Williams (1989, p.134) retained Xanthidium (as Hystrichokolpoma) bulbosum. The validity/authorship of this name may need to be reconsidered as it appears that Ehrenberg (1837b) did not provide a description.

Holotype: Ehrenberg, 1838, pl.1, fig.16
Age: Late Cretaceous?