Hystrichosphaera pilosa (Ehrenberg, 1854, pl.37, section 8, fig. 4) Wetzel, 1933b, p.43. Emendation: Erkmen and Sarjeant, 1980, p.50, as Sentusidinium pilosum.

Combination not validly published: generic name not validly published until 1937.
NOW Barbatacysta pilosa. Originally Xanthidium pilosum (acritarch), subsequently Hystrichosphaera pilosa (combination not validly published), thirdly Hystrichosphaeridium? pilosum, fourthly Baltisphaeridium pilosum (acritarch), fifthly Ovum hispidum subsp. pilosum (combination not validly published; acritarch), sixthly Cleistosphaeridium pilosum (combination not validly published), seventhly Tenua pilosa, eighthly Sentusidinium pilosum, ninthly Batiacasphaera pilosa, tenthly (and now) Barbatacysta pilosa.
The validity/authorship of this name may need to be reconsidered as it appears that Ehrenberg (1854) did not provide a description.

Holotype: Ehrenberg, 1854, pl.37, fig.8, no.4
Locus typicus: Krakow, Poland
Stratum typicum: Corallian (Oxfordian)

Diagnosis: Sarjeant, 1968, p.231: Xanthidium pilosum
Shell elongate ovoidal to ellipsoidal, the apex most often lost. Spines very numerous (in excess of 500), short (between one-quarter and one eight of the shell breadth), tapering from the base, pointed or capitate distally but always closed. They are hollow, the spine cavity connecting with the shell interior.
Dimensions: Holotype: overall length 53 µm. Range of English specimens: overall length 40-60 µm. Range of French specimens: overall length (apex lacking) 34-38 µm, breadth 34-36 µm, shell length 30-31 µm, breadth 30-31 µm.