The Echinoid Directory

Gymnechinus Mortensen, 1903, p. 115

Diagnostic Features
  • Small, low hemispherical test.
  • Apical disc with ocular plates I and II insert; periproct distinctly displaced to the rear right-hand side (ocular plate I).
  • Ambulacral plating trigeminate; each ambulacral plate with a primary tubercle and a smaller inner secondary tubercle. Pore-pairs offset in arcs of three forming a single adradial band.
  • Interambulacral plates with distinct primary tubercle and flanking secondary tubercles almost as large as primary; in some species forming horizontal series at the ambitus.
  • Aboral surface rather naked.
  • Peristomial membrane devoid of plates other than the 10 buccal plates.
  • Auricles separate.
Recent; Indo-West Pacific.
Name gender masculine
Echinus robillardi de Loriol, 1883, p. 23, by original designation.
Species Included
  • G. robillardi (de Loriol, 1883); Recent, Indian Ocean, Littoral to 70m.
  • G. pulchellus Mortensen, 1904; Recent, West Pacific; 5-50 m.
  • G. epistichus Clark, 1912; Recent, Philippines, Littoral to 35 m.
  • G. abnormalis Clark, 1925; Recent, Indian Ocean, 54 m.
Classification and/or Status

Euechinoidea; Camarodonta; Temnopleuroida.

Subjective junior synonym of Pseudechinus.


Distinguished from all other genera in this family by the strongly asymmetric position of the periproct and hemicyclic disc, and by the naked peristomial membrane.

Mortensen, T. 1903. The Danish Ingolf-Expedition 1895-1896. Vol. 4, No. 2. Echinoidea, pt. 1, 198 pp., 21 pls. Bianco Luno, Copenhagen.

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