The Echinoid Directory

Hemicentrotus Mortensen, 1942, p. 231

Diagnostic Features
  • Test rather flattened in profile and thick-plated.
  • Apical disc hemicyclic; posterior oculars generally insert.
  • Ambulacra polygeminate with pore-pairs in arcs of four, tending to form distinct vertical series. Each ambulacral plate with a primary tubercle.
  • Ambulacral pore zones uniform; not expanding as phyllodes but narrowing towards the peristome.
  • Interambulacral plates with a primary tubercle and two or three slightly smaller secondary tubercles forming a distinct horizontal series. No adapical naked zone interradially.
  • Spines short (less than 1/4 test diameter).
  • Globiferous pedicellariae with muscular neck and no lateral teeth.
  • Buccal notches small and indistinct.
Distribution
Recent; Japan and China; 0-45 m.
Name gender masculine
Type
Psammechinus pulcherrimus A. Agassiz, 1863, by original designation.
Species Included
  • Only the type species.
Classification and/or Status

Camarodonta; Echinoida; Strongylocentrotidae.

Monotypic.

Remarks
A well characterized genus.