Merriam-Webster Collegiate Dictionary - saxitoxin

 noun  Etymology: saxi- (from New Latin Saxidomus giganteus, species of butter clam from which it is isolated) + toxin  Date: 1962 a potent nonprotein neurotoxin C10H17N7O4•2HCl that originates especially in dinoflagellates (genus Gonyaulax) found in red tides and that sometimes occurs in and renders toxic normally edible mollusks which feed on them