Abstract:
Five echinoid species are described from the upper Miocene part of the Yorktown Formation of Virginia: Echinocardium orthonotum (Conrad), Arbacia imporcera (Conrad), Psammechinus philanthropus (Conrad), Mellita aclinensis Kier, and Spatangus glenni Cooke. The assemblage probably lived in shallow, warm-temperate waters, E. orthonotum deeply buried near shore, S. glenni shallowly buried offshore, and M. aclinensis with its test just covered near shore. Arbacia improcera and P. philanthropus presumably lived together intertidally and near shore, P. philanthropus living in holes in the indurated sediments or on the sand with its test covered with debris, whereas A. improcera probably was easily visible with nothing covering its test. Specimens formerly referred to E. orthonotum from the middle Miocene Choptank Formation from Maryland are referred to E. marylandiense, new species. Echinocardium gothicum (Ravenel), from the Bear Bluff Formation of South Carolina, is considered a junior subjective synonym of E. orthonotum.
