The Echinoid Directory

Acrocircus Lambert, 1911, p. 171 (11)

Diagnostic Features
  • Test depressed in profile, with ambitus a little below mid-height; weakly domed above. Slightly sunken towards peristome.
  • Apical disc firmly bound to corona; monocyclic; periproct proportionallyt very large, with smooth rounded outline.
  • Ambulacra straight, about half as wide as interambulacra. Plating trigeminate, compound style unknown. Pore-pairs uniserial throughout.
  • Single adradial primary tubercle to each compound plate plus smaller secondary perradial tubercle at the ambitus.
  • Interambulacral plates with single central primary tubercle, with slightly incised areole; flanked by smaller adradial and interradial secondary tubercles.
  • Interradial zone rather sparsely tuberculate adapically.
  • Primary tubercles imperforate and crenulate.
  • Peristome about half test diameter; buccal notches small but distinct.
  • Spines and lantern unknown.
Upper Eocene; France.
Name gender masculine
Micropsis biarritzensis Cotteau, 1863, p. 65, by original designation.
Species Included
  • Only the type species.
Classification and/or Status

Euechinoidea, Camarodonta; unnamed family (triplacidiids)

Monophyletic. Subjective junior synonym of Triplacidia.


Lambert quickly revised his opinion on the utility of this genus and in the same year (Lambert & Thiery 1911, p. 215) treated Acrocircus as a synonym of  Triplacidia.

Lambert, J. 1911. Notes sur quelques Echinides eoceniques des Corbieres septentrionales. Annales de la Universite Lyon Serie 1, fasc. 30, p. 171.

Cotteau, G. 1863. Paleontologie Francaise. 18. Terrains Tertiairies. Eocene Echinides II. G. Mason, Paris. (pl. 329).

Lambert, J. & Thiery, P. 1909-1925. Essai de nomenclature raisonnee des echinides. Chaumont, Ferriere.

Mortensen, T. (1943) A monograph of the Echinoidea Part III.2, Camarodonta 1. C. A. Reitzel, Copenhagen.