Why do sand dollars have holes?

So..probably everyone has SEEN sand dollars or knows what a sand dollar is. ... And am looking forward to learn about those sand dollars without holes. ... read more

Any sand dollar you look at will always have two holes. These are the mouth and anus. The image of the sand dollar below (by B.Navez via Wikipedia) shows the top view on the left and the bottom view on the right. read more

The Keyhole sand dollar got its common name from the intriguing slot-shaped holes in the body (called lunules). Suggestions for the function of these slots range from helping the animal to burrow, right itself, find food or to prevent the waves from lifting it out of the sand. read more