Echinoida

Echinoida is an order of sea urchins in the class Echinoidea. They are distinguished from other sea urchins by simultaneously possessing both an un-sculpted test and a feeding lantern with large plates fused across the top of each pyramid.

Taxonomy
Order Echinoida
 * family Echinidae Gray, 1825
 * family Echinometridae Gray, 1825
 * family Parasaleniidae
 * family Strongylocentrotidae Gregory, 1900