Echinoid a. : Of or pertaining to the Echinoidea.

Echinoid n. : One of the Echinoidea.

Example:
what is an Echinoid? Where can I find them in north texas?

Taxonomy
sea urchin, echinoids, spines, urchins, Superorder, test, dangerous spines, species, fossils, tube feet, Subclass, Cretaceous period, free encyclopedia, pencil, heart urchins, spiny, class Echinoidea, humans.

Defination from the web:
echinoid diversity, and this trend continued to the Permian period. ... The Echinoid Directory from the Natural History Museum. Echinoids of the North Sea ...