Palaeohystrichophora brevispinosa Pocock, 1962, p.81, pl.14, figs.222–223. Emendation: Brideaux, 1977, p.15–16, as Tenua brevispinosa.

Now Circulodinium. Originally Palaeohystrichophora, subsequently Tenua Eisenack, 1958, thirdly Canningia?, fourthly Cyclonephelium, fifthly (and now) Circulodinium

Holotype: Pocock, 1962, pl.14, fig.222; Jansonius, 1986, pl.4, fig.6; Fauconnier and Masure, 2004, pl.14, figs.7–8.
Paratype: Pocock, 1972
Locus typicus: Imperial Virginia Hills, W Canada
Stratum typicum: Barremian

Original description: Pocock, 1972, p. 81:
Theca more or less isodiametric, covered by short spines; transverse furrow equatorial, broad, marked by two rows of short spines; epitheca conical, terminated by a tuft of slightly longer spines than those covering the rest of the theca; epitheca terminated by two short blunt processes, one slightly longer and sharper than the other; the theca commonly encloses a spherical cyst about half the diameter of the theca; yellow green spherical organic bodies are also frequently present.
Size range: Theca: Width of girdle 69 (98) 110 µm X 110 (114) 120 µm.
Spine length: a. at epitheca 5 (6) 7 µm. b. at girdle 3 (3.5) 5 µm. c. body of theca 2 (4) 6 µm. Diameter of cyst 48 (55) 63 µm.