The Echinoid Directory

Ctenocidaris ( Eurocidaris ) Mortensen, 1909, p. 3

Diagnostic Features
  • Test low and rather thin-plated.
  • Apical disc and peristome about 50% test diameter; dicyclic (usually); plates generally covered in tubercles. Ocular pores rimmed. Sexual dimorphism in gonopore size; gonopores large and marginal in females, in part bounded by interambulacral plates.
  • Interambulacra of relatively few plates (up to 8). Tubercles perforate and non-crenulate with sunken areoles. Scrobicular circle not strongly differentiated from other secondary tubercles; outside areole plate uniformly covered in secondary tubercles with narrow incised interradial suture and feeble pits at triple suture junctions.
  • Ambulacra almost straight. Pore-pairs very small and oblique, with the two pores separated by a very narrow interporal partition. Primary and smaller secondary tubercle to each ambulacral plate. Pore zones not sunken.
  • No naked perradial zone or pits developed.
  • Peristome with well developed series of ambulacral plates.
  • Primary spines long, cylindrical, with short collar and distinct neck. Shaft ornamented with irregular thorns and with dense fine hairs in between. In some species spines become spatulate distally.
  • Oral spines simple; not widened or serrate.
  • Secondary spines with swollen tip.
Recent; Subantarctic.
Name gender feminine
Cidaris nutrix Wyville Thomson, 1876, p. 62, by original designation.
Species Included
  • Only the type species.
Classification and/or Status

Cidaroida; Ctenocidaridae.

Treated as subgenus of Ctenocidaris by Mortensen(1928).


The only character that distinguishes Eurocidaris from Ctenocidaris is that its oral primary spines are simple and undifferentiated; those of Ctenocidaris being decidedly serrate and spear-shaped.

Mortensen, T. 1928. A monograph of the Echinoidea. 1, Cidaroidea. C. A. Reitzel, Copenhagen.