Richmondian  search
BTChronostratigraphic Units
 .Phanerozoic
 ..Paleozoic
 ...Ordovician
 ....Upper Ordovician
 .....Cincinnatian
 ......Richmondian
SNNorth America. Upper Ordovician, above Maysvillian and below Lower Silurian. Added to Thesaurus in 1985.