Geological Survey Professional Paper

7½-minute quad angle formed anteriorly and posteriorly Atlantic Coastal Plain auricles along line auricular denticles beach level Bivalvia byssal notch Calvert County Calvert Formation Camp Conoy center of resilial Chesa Chesapeake Bay Chesapecten jeffersonius Chesapecten madisonius Chesapecten middlesexensis Chesapecten nefrens Chlamys Lyropecten Cobham Wharf Convexity of left Cove Point Creek ctenolium denticles disk flanks edge of disk exterior sculpture figures formed by lines fossil genus growth at beak height holotype James River jeffersonius Say lectotype left valve length of auricle line of ligament lines through origin Maryland Marys Formation Marys River miles 3.2 km minute quad Miocene origin of shell paratype Pecten Chlamys Pecten jeffersonius Pectinidae plate Pliocene ribs right bank santamaria Tucker Say's scabrous lirae septenarius Say Shattuck shell growth shore of Chesapeake small gapes sonius species Specimen LN HT specimens of Chesapecten stratigraphic striae tangent tion upper Virginia St Urbanna USGS loc USNM Yorktown Formation