Related Clues:

• Silent ___ (time before the talkies)
• Mellow, as cheese
• An earlier one may be recalled
• Paleontologist's estimate
• Many moons
• Secret stat, sometimes
• Paleozoic, for one
• Geological time division
• Historical stage
• Ruth's was 2.28
• Unique stretch in time
• Paleozoic, for example
• --- of Good Feelings
• Several periods
• Twain's "The Gilded ---"