Perischoechinoidea

Perischoechinoidea

[pə¦ris·kō‚ek·ə′nȯid·ē·ə]
(invertebrate zoology)
A subclass of principally extinct echinoderms belonging to the Echinoidea and lacking stability in the number of columns of plates that make up the ambulacra and interambulacra.