Brachiopods, commonly called "lamp shells," are a phylum of two-shelled marine organisms that have existed since the Cambrian period. They resemble clams but differ anatomically, with symmetrical shells of unequal size. Clams have asymmetrical shells of equal size. Brachiopods filter nutrients from sea water and live in the very cold water of polar regions or at great depths, although in the past, particularly the Mississippian period in which they were abundant, they inhabited warmer, shallower waters.
Courtesy of Kentucky Paleontological Society