SriCTOPORA PALMIPE8, Hall. 



Fig. 20. A frond, natural size. 



Hamilton group. Weio York. 



CYSTODICTYA. 



(Page 536.) 

 Cystodictya incisurata, Hall. 

 Fig. 11. A transverse section of a branch. x6. 

 Hamilton group. Kevj York. 



CY^TODICTYA QIIBBRTI, Mcck. 



Fig. 12. A portion of a frond from which the surface has been worn 



away, showing the cell tubes. x6. 

 Fig. 13. A fragment of a frond, natural size. 

 Fig. 14. A natural vertical section showing the cell tubes, and in 



some of them the sept?e. x6. 

 Fig. 15. A natural transverse section. x6. 

 Fig. 16. An enlargement of the mesotheca, showing the transverse 



arching lines of growth and the longitudinal lines formed 



by the recumbent portion of the cell tubes. x6. 

 Fig. 17. An enlargement showing the cell apertures with denticulated 



projections. x6. 

 Upper Helderberg group. Falls of the Ohio. 



Cystodictya ovatipora, Hall. 

 Fig. 18. A portion of a frond, natural size. 

 Fig. 19. The same. x6. 



Upper Helderberg group. Falls of the Ohio. 



639 



