(n.) Any one of numerous species of echinoderms of the order Echinoidea.

Loch Ness monster alevin benthon benthos cetacean crustacean dolphin dugong fingerling fish fry game fish grilse harbor seal kipper man-eater man-eating shark manatee minnow minny nekton octopus panfish plankton porpoise salmon sea dog sea lion sea monster sea pig sea serpent sea snake sea urchin seal shark shellfish smolt sponge squid tropical fish walrus whale