The Echinoid Directory

Key to the families of Stegasterina

1a. Test thick and flat-based; periproct marginal with distinct subanal bulge. Ambulacral plates much lower than interambulacral plates aborally.

Stegasteridae

1b. Test usually thin and always inflated; periproct marginal to inframarginal without subanal bulge. Ambulacral and interambulacral plates similar in size aborally.

Calymnidae