Hebertella is a common fossil brachiopod found in Upper Ordovician rocks. Commonly called "lamp shells," brachiopods are two-shelled marine organisms that have existed since the Cambrian period. They differ from clams in that they have symmetrical shells of unequal 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 they inhabited warmer, shallower waters.

Courtesy of the Kentucky Paleontological Society