CHEWTONIAN STAGE

division of time within the Ordovician Period in Australia and New Zealand (the Ordovician Period began about 505 million years ago and lasted about 67 million years). The Chewtonian Stage follows the Bendigonian Stage and precedes the Castlemainian Stage. Several zones, shorter spans of time, are recognized within the Chewtonian Stage and are based upon the vertical ranges of several species of fossil graptolites of the genera Didymograptus and Tetragraptus. These forms allow correlations to be made with rocks in North America and Europe.