Where do Sand Dollars come from? Do they hold an animal inside like clams?

Sand Dollars are most like sea urchins, or the little prickly balls that you find at the bottoms of oceans. When they are alive, they have small, tiny spines that surround the entire shell, making it feel like velvet. When you see them washed up and dead on the beach, you can't feel the velvety 'skin' and spines on their shell because of their exposure to the sun. Sand Dollars are also found at the bottoms of oceans, and in shallow salt waters they are found just beneath the surface of sandy or muddy areas. Sand Dollars aren't plants, they are marine animals. And no, they don't hold an animal inside, but they are still a treasure! :D In fact, they got their name 'sand dollar' because people used to think that they were mermaid money.

Hope this helps!

Sand dollar itself is a living creature...an animal
http://en.wikipedia.org/wiki/Sand_Dollar

What Do Sand Dollars Do

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RE:
Where do Sand Dollars come from? Do they hold an animal inside like clams?
Where can they be found?

Sand dollars come from a type of jelly fish that wash up on the beach and dry in the sand, if you keep one long enough the sand will stop sticking together and drop off as the jelly dries up

Sand dollars are the skeletal remains of a sea creature that are similar to urchins. It funnels sand through its "mouth" to remove food and "spits" the sand out its "other end".

The remains rattle from loose bone structures inside. If you break open the outer "shell", these bones look like birds.

I've always found them on the Eastern/Gulf U.S. shores.

Like the last person said, sand dollars are animals themselves. They belong to the same phylum (Echinoderms) as sea stars and sea urchins but are more closely related to sea urchins.