The
Drumian is a stage of 3rd series of the
Cambrian. It succeeds still unnamed 5th stage of the Cambrian and precedes the
Guzhangian. The base is defined as the first appearance of the
trilobite Ptychagnostus atavus around million years ago. The top is defined as the first appearance of another trilobite
Lejopyge laevigata around million years ago.