Word Meanings - ECHINIDAN - Book Publishers vocabulary database

One the Echinoidea.

ECHINOIDEA
The class Echinodermata which includes the sea urchins. They have a calcareous, usually more or less spheroidal or disk-shaped, composed of many united plates, and covered with movable spines. See Spatangoid, Clypeastroid.
PALEECHINOIDEA
An extinct order of sea urchins found in the Paleozoic rocks. They had more than twenty vertical rows of plates. Called also Palæechini.