The Echinoid Directory

Helgocystis Mortensen, 1907, p. 82

Diagnostic Features
  • Test subcylindrical with strong posterior rostrum; thin-shelled.
  • Apical disc with four gonopores. Compact, with single anterior plate bearing two gonopores (G2) and two postero-lateral plates each with a gonopore (ocular plates II and IV). Posterior genital plates rudimentary and in contact with posterior ocular plates.
  • Ambulacra all similar with minute pores only outside oral region. Double pores close to peristome.
  • Anterior ambulacrum deeply sunken from ambitus adorally, forming a funnel-like opening to the peristome.
  • Peristome subcircular and facing anteriorly into frontal groove.
  • Plastron plating orthosternous; first sternal plate enlarged and followed by a pair of symmetrical episternal plates.
  • Plastron plating not disjunct. Interambulacra 1 and 4 disjunct, plates not reaching peristome.
  • Ambulacra I and V continuous on oral surface; not separated by intercalated plates of interambulacra 1 and 4.
  • Scattered small tubercles distributed over the aboral surface.
  • Periproct supramarginal, overarched by interambulacral plates.
  • Subanal fasciole present.
Distribution
Recent; Antarctic and subantarctic.
Name gender feminine
Type
Pourtalesia carinata A. Agassiz, 1879, p. 205, by original designation.
Species Included
  • Only the type species.
Classification and/or Status

Holasteroida, Meridosternata, Urechinina, Pourtalesiidae.

Monotypic.

Remarks

Differs from Pourtalesia which is very similar in shape, in having ambulacra I and V continuous on the oral surface and not interrupted by interambulacral plates from Ia 1 and 4, as in Pourtalesia.

Mortensen, T. 1907. The Danish Ingolf-Expedition 1895-1896. Vol. 4, No. 2. Echinoidea, pt. 2. Bianco Luno, Copenhagen.

Mortensen, T.1950. A Monograph of the Echinoidea. V.1. Spatangoida 1. C. A. Reitzel, Copenhagen.