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SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 68 



that Kentucky was a land area during the deposition of the Middle 

 and Upper Black River strata, and that the line AB therefore, marks 

 an unconformity of deposition. This is also evidenced by numerous 

 worm burrows extending downward from the top of the white 

 limestone. When the material was in the condition of soft mud and 

 exposed at the surface, the worms burrowed into it as they do in the 

 soil to-day. 



Fig. 2S. — Phosphate mine of Wallace, Ky., showing occurrence of phosphate 

 rock along joint planes of limestone. Photograph by Bassler. 



The phosphate localities near Wallace, Kentucky, were next visited 

 in order to obtain illustrations of the gradual phosphatization of 

 limestone and the types of fossils in phosphatic strata. Here it was 

 discovered that phosphate rock occurs only along the joint planes 

 of the limestone, as shown in figure 2^. Surface water passing along 

 these joint planes leaches out the calcium carbonate of the phosphatic 

 limestone, leaving the calcium phosphate content behind, as is well 

 shown in the photograph. The piece of phosphatic limestone at C 

 was removed and shipped to Washington for exhibition. Here also 



