Carrie Hartman, age 12, of Beaumont, Texas, for her question:

WHAT IS A LAMPSHELL?

Lampshell is the common name for members of the phylum Brachiopoda, a small marine animal with two shells.

Formerly classified in the same phylum as mollusks, lampshells differ from them in that the shells lie dorsally and ventrally instead of left and right, and the enclosed organism has an arm like appendage on each side of the mouth.

Lampshells were a dominant form of life in earliest geological times but since the close of the Paleozoic Era, they have been steadily decreasing. Although more than 4,000 species are known, only 220 of these are living today. The rest are found only as fossils.

Most living lampshelis live at moderate depths, sometimes down to 1,500 feet. Most are less than one inch across.

The phylum is generally grouped into two classes: the articulata, which have hinged shell valves, and the inarticulate, which do not have hinges.