Related Clues:

• Times and Guardian editors selected leaders therefrom
• Twenty bajillion years
• An awfully long time
• Millions of lifetimes
• Great geological time span
• Geological age
• Quasi-opposite of ''flash''
• Proterozoic ___
• ". . . for children of all ___!"
• Turns mellower
• "Rock of __"
• Yonks
• Geologist's unit
• Puts on years
• Many, many epochs