Chesapecten Jeffersonius fossil scallop measuring 6 in. (length) x 5.5 in. (height). Outer anterior edge has some loss of shell material and there is a 1.625 in. crack extending up from the umbo/hinge. Gift of Gerald H. Johnson, Professor Emeritus of Geology. EDU2014.009 Background information provided by Professor Johnson: "The Jefferson scallop was first described by Martin Lister in 1687. Thomas Say officially named it Pecten jeffersonius in 1824. Ward and Blackwelder erected a new genus of fossil scallops, Chesapecten, in 1975 and assigned the Jefferson scallop to it. Later the Virginia State Legislature adopted Chesapecten jeffersonius as the state fossil of Virginia upon the urging of staff at the Virginia Natural History Museum and members of the College of William and Mary community. "The state fossil is found in the lower part of the Yorktown Formation, a shelly sand with a diverse fossil fauna. The Yorktown crops out along rivers in eastern Virginia. Chesapecten jeffersonius lived on a shallow, wave-swept sea floor during the early Pliocene Epoch, about 4 million years ago. Most shells are preserved in their original state, and are composed of the minteral calcite. Many scallops have fossil borings made by snails, worms, clams, 'moss animals' and algae, and also may have barnacles, corals and other organisms attached to their shells."