ILLINOIS STATE GEOLOGICAL SURVEY. 



MONOGRAPH No. 1. PLATE LXXXI. 



10 



11 



12 



13 



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16 17 18 19 2O 14 15 



21 22 



23 



'9^^ 



24 



25 26 



48 



27 28 29 



30 







52 53 



54 



35 



46 47 



W ll f 



36 



44 45 41 



42 38 



