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Sea Shells and Sea Biscuits

I know that sea biscuits are living animals, but is the shell of a sea biscuit considered a sea shell? Thank you.

Wildlife Expert - Ken Burton

Your question begs a bigger one: What IS a seashell? Encarta defines a seashell as "the empty shell of a sea creature, especially a mollusk." Sea biscuits, as you may know, are echinoderms, not mollusks, but they certainly are sea creatures. The hard part that washes up onto beaches is called a "test," which is really a skeleton more than a shell. So I suppose technically, no, it's not a seashell, but very few beachcombers would make the distinction.

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