Article: The echinoids Micraster and Epiaster from the Turonian and Senonian of England
Robert B. Stokes
A revised nomenclature and stratigraphical distribution are recorded for species of the spatangoid genera Epiaster and Micraster from the Turonian and Senonian of southern England. Distinguishing characters of the species are summarized, and the names E. michelini, E. laxoporus, M. normanniae, M. decipiens, M. coranguinum simpsoni, and M. westlakei advocated for British material. The old cortestudinarium Zone is here replaced by a lower normanniae Zone, of probable Turonian age, and an upper decipiens Zone, of Coniacian date. These new zones are denned in the Dover cliffs, where the base of the planus Zone, here redefined on the basis of spatangoid faunas, is held to correspond with the base of the Chalk Rock.