The Echinoid Directory

Family Hemicidaridae Wright, 1857, p. 68


 Carinacea with:

  • apical disc relatively small; dicyclic to hemicyclic; firmly bound to corona. Periproct subcircular with smooth edges (no intercalated periproctal plates);
  • ambulacra trigeminate to polygeminate, with all elements extending from adradial to perradial suture. Sometimes simple adapically;
  • pore-pairs uniserial at ambitus and above; crowded to form phyllodes adorally;
  • primary tubercles in ambulacral zones significantly smaller than those of interambulacral zones; interambulacral tubercles perforate and usually crenulate;
  • peristome much larger than apical disc; with deep, open buccal notches.
Middle Jurassic to Lower Cretaceous, Europe, North Africa, Middle East, India, Madagascar.
Species Included There are two subfamilies, Hemicidarinae and Pseudocidarinae, included here
Classification and/or Status Euechinoidea, Acroechinoidea, Carinacea
Like acrosalenids in having ambulacral tubercles very much smaller than interambulacral tubercles, perforate and crenulate tubercles and acrosaleniid-style plate compounding with all elements extending to the perradius, but differing in having a rounded periproct without angular elements forming an integral part of the apical disc circlet.

Wright, T. 1855-1860. Monograph of the British fossil Echinodermata of the Oolitic formations. I. Echinoidea. Monographs of the Palaeontographical Society. 481 pp.