EXPLANATION TO PLATE 4. 



(Showing the development of the shell and its spinosity.) 



HOLSTON RIVER SYSTEM — continued. 



Figs. 1-13. Lot 94. Group 13. Bluff City, Tenn. Enlarged 1/6. 



Figs. 14-20. Lot 88. Group 16. Rogersville, Tenn. Enlarged 2/5. 



Figs. 21-34. Lots 87 and SS. Group 16. Rogersville, Tenn. Natural size. 



Figs. 35-47. Lot 90. Group 17. Cobb Ford, Tenn. Natural size. 

 100 



