18 ILLUSTRATIONS 



FIGURE PAGE 



1. Columnar section of the Cambrian, Ozarkian, and Canadian strata of 



Maryland 48 



2. Columnar section of the Ordovician rocks of Maryland 49 



3. Cambrian-Ordovician Correlation Table 51 



4. Paleogeographic map of Lower Cambrian (Waucoban) 55 



5. Paleogeographic map of Middle Cambrian (Acadian) 55 



6. Paleogeographic map of Upper Cambrian (St. Croixan) 75 



7. Paleogeographic map of Early Ozarkian (Conococheague) 75 



8. Paleogeographic map of Upper Ozarkian (Copper Ridge) 79 



9. Paleogeographic map of Late Ozarkian (Chepultepec) 79 



10. Paleogeographic map of Lower Canadian (Bretonian) 91 



11. Paleogeographic map of Middle and Late Canadian (Beekmantown) . 91 



12. Structure Sections across Frederick Valley 112 



13. Paleogeographic map of Early Ordovician (St. Peter) 119 



14. Paleogeographic maps of Early Ordovician (Mosheim) 119 



15. Paleogeographic map of Early Ordovician (Middle Stones River) 



Maclurites magnus fauna 125 



16. Paleogeographic map of Early Ordovician (Upper Stones River) 125 



17. Diagrammatic section of Chambersburg limestone from Chambers- 



burg, Pa., to Strasburg, W. Va 131 



18. Paleogeographic map of Early Ordovician (Blount) 134 



19. Paleogeographic map of Middle Ordovician. Lower Black River 



(Lowville) 134 



20. Paleogeographic map of Middle Ordovician. Middle Black River 



(Decorah) 138 



21. Paleogeographic map of Middle Ordovician. Upper Black River 



(Kimmswick) 138 



22. Paleogeographic map of Middle Ordovician. (Latest Chambersburg) . 155 



23. Paleogeographic map of Middle Ordovician (Early Trenton) 155 



24. Paleogeographic map of Late Ordovician. Early Cincinnatian 



(Utica) 159 



25. Paleogeographic map of Late Ordovician. Cincinnatian (Eden) 159 



26. Paleogeographic map of Late Ordovician. Cincinnatian (Fairview) . 162 



27. Paleogeographic map of Late Ordovician. Cincinnatian (Oswego or 



McMillan) 162 



