THE PLANKTON OF SHAWNEE CAVE. 



395 



V7 



TYPE I. 



TYPE II. 



TYPE III. 



Diagrammatic section of compound and simple sink holes. I, original opening ; 

 2, obstruction ; 3, impervious layer of clay; 4, second opening; 5, ordinary water- 

 level ; 6, flood water-level ; 7, subterranean passage. 



