PILEOTRYPA. 



(Page 562.) 



PiLEOTRYPA CLIVULATA, Hall. 



Fig. 8. An enlargement of a vertical section, showing the oblique cell 

 tubes and intercellular vesicles.- 

 Upper Helderberg group. Falls of the Ohio, 



PiLEOTKYPA PYRIFOBMIS, Hall. 



Fig. 9. An enlargement of the surface. x6. 



Fig. 10. A still further enlargement, showing more distinctly the 



character of the cell apertures. xl8. 

 Fig. 11. An oblique view of a portion of the surface. x6. 

 Upper Helderberg group. Falls of the Ohio. 



PiLEOTRYPA DENTICULATA, Hall. 



Fig. 12. An enlargement of the surface, showing the form and 

 arrangement of the cell apertures and the maculae of larger 

 cells. x6. 

 Upper Helderberg group. Falls of the Ohio, 



PiLEOTRYPA GRANIFEEA, Hall. 



Fig. 13. An enlargement of the surface. xlS. 



Upper Helderberg group. Falls of the Ohio. 



PiLEOTRYPA BI8TBIATA, Hall. 



Fig. 14. An enlargement of the surface, showing the form and 

 arrangement of the cell apertures, and one of the maculae. 

 x6. 

 Upper Helderberg group. Falls of the Ohio. 



PiLEOTRYPA GEOMETEICA, Hall. 



Fig. 15. An enlargement, showing the form and arrangement of the 

 cell apertures and one of the maculae. x6. 

 Upper Helderberg group. Falls of the Ohio. 

 84 



665 



