From Coastal Wiki
Definition of Echinoidea:
class of echinoderms, commonly called sea urchins, having a typically globular body with skeletal plates fitting together to form a rigid test.
This is the common definition for Echinoidea, other definitions can be discussed in the article
- ↑ Lawrence, E. (2005). Henderson’s dictionary of biology. Pearson Education Limited, 13th ed., Harlow. 748 p.