PeISMOPORA SUBTRIQUETRA, Hall. 



Fig. 15. A portion of one of the faces of a branch. x6. 

 Upper Helderberg group, ^alls of the Ohio. 



SCALARIPORA. 



(Page 532.) 

 SCALARIPORA. sc alasiformis, Hall. 



Fig. 16. A specimen, natural size. 



Fig. 17. An enlargement of the concave face of a branch. x6. 



Fig. 18. An oblique view of the same, showing the form of the scalae. 



x6. 

 Fig. 19. An enlargement of the two narrower faces of a frond. x6. 

 Fig. 20. A transverse section, showing the radiating mesothecae, the 



cell tubes and the form of the scalae. x6. 

 Upper Helderberg group. Falls of the. Ohio. 



Scalaripora subconcava, Hall. 

 Fig. 21. A fragment, natural size. 

 Fig. 22. A transverse sectiou; x6. 



Upper Helderberg group. Falls of the Ohio. 



643 



