 Marine gastropods in the predatory superfamily Conoidea , ( known as the toxoglossans , meaning " poison tongue " ) use a poison dart or harpoon , which is a single modified radula tooth which is created inside the mouth of the snail , and which is primarily made of chitin . These snails are carnivorous hunters : the harpoon is used in predation . When the snail is close to its prey , it extends its proboscis a considerable distance ; then it fires its harpoon and injects a toxin into the prey . For most species of toxoglossans the prey is marine worms , but in the case of some larger cone snails , the prey is small fish . 
