Crossword Puzzle

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Across
  1. 2. Period in Earth's history
  2. 5. A major division of geologic time
  3. 7. Oldest era; organisms developed hard parts
  4. 8. Largest extinction in Earth's history
  5. 10. Formation of oceans, atmosphere, and continents; bacteria
  6. 11. period characterized by the greatest development, rise of modern insects and flowering plants
  7. 12. Prehistoric period during which stone was widely used
Down
  1. 1. record of earths history
  2. 3. Numerous fishes, other sea life; many plants, first trees; wingless insects
  3. 4. oldest and longest geologic time period
  4. 6. a cold-blooded vertebrate including snakes and lizards
  5. 9. Numerous fishes, other sea life; many plants, first trees; wingless insects