Atrypa (lampshell) is an extinct genus of brachiopod from the Late Ordovician stage (444 million years ago) to the Carboniferous stage (318 mya). It occurs abundantly as fossils in marine rocks. Fossils have been found on all continents except Antarctica.
This animal has distinctive concentric growth lines and is unusual in that in some Devonian beds there are numerous remains of the pedicle (foot) valve, but very few of the brachial (upper) valve — scientists speculate that strong ocean currents may have played a role in this.
Several species of Atrypa have been described.
Image Caption: Atrypa reticularis – Plate from James D. Dana – New Text-Book of Geology (New York: Ivison, Blakeman & Company, 1883). Credit: James Dwight Dana/Wikipedia