PLATE I. 



RETEPORELLA. 



(Page 503.) 

 Retepoeella undulata, Hall. 



Figs. 1, 2. Natural size. 



Fig. 3. Celluliferous face. x6. 



Upper Helderberg group. Falls of the Ohio. 



Retepoeella adnata, Hall (sp.). 

 Fig. 4. Noncelluliferous face. x6. 

 Fig. 5. Celluliferous face. x6. 



Upper Helderberg group. Falls of the Ohio. 



RETEPORINA. 



(Page 504.) 

 Reteporina striata, Hall. 



Fig. 6. Noncelluliferous face. x6. 

 Fig. 7. Celluliferous face. x6. 



Hamilton group. New York. 



Reteporina perundtjlata. Hall. 



Fig. 8. Noncelluliferous face. x6. 



Upper Helderberg group. Falls of the Ohio. 



POLYPORELLA. 



(Page 503.) 

 Polyporella fistulata. Hall (sp.). 



Fig. 9. Transverse section. x6. 

 Fig. 10. Celluliferous face. x6. 



Hamilton group. New York. 



POLYPORA. 



(Page 502.) 

 Poltpora aspectans. Hall. 



Fig. 12. Transverse section. x6. 

 Fig. 13. Celluliferous face. x6. 



Upper Helderberg group. Falls of the Ohio, 



Poltpora striatopora, Hall. 

 Fig. 11. Natural size. 

 Fig. 14. Celluliferous face. x6. 

 Fig. 15. Noncelluliferous face. x6. 



Upper Helderberg group. Falls of the Ohio. 



620 



