Marie Danneker, age 14, of West St. Paul, Minn., for her question:

WHAT IS A SAND DOLLAR?

A sand dollar looks a bit like a silver dollar or a cookie. It is actually an animal that lives in shallow coastal waters. About two to four inches wide, it is quite flat and thin with a circular body.

Some sand dollars can be notched at the top, while others have slots. The top surface holds a set of breathing tubes that are arranged in the form of a five pointed star. The body of the sand dollar is covered with tiny movable spines which are used for clawing and digging.

A sand dollar lives buried not too deep in sand. It eats tiny bits of plants and animals found among the grains of sand. The mouth is in the center of the under surface. Like the starfish and the sea urchin, the sand dollar is an echinoderm.