PLATE IV. 

 PTILOPORELLA. 



(Page 506.) 

 Ptiloporella inequalis, Hall. 



Fig. 1. A fragment of a specimen, natural size. 

 Fig. 2. An enlargement of a portion of the preceding figure. x6. 

 Upper Helderberg group. Walpole, Ontario. 



Ptiloporella laticrescens, Hall. 

 Fig. 3. A fragment, natural size. 

 Fig. 4. A transverse section of ttie branches. 6x. 

 Fig. 5. An enlargement from the noncelluliferous face of a frond, 



showing two of the primary branches. x6. 

 Fig. 6. An enlargement from the celluliferous face of Fig. 3, showing 

 the form and arrangement of the cell apertures. 

 Upper Helderberg group. WalpoU^ Ontario. 



PINNAPORINA. 



(Page 507.) 



PiNNAPORINA PINNATA, Hall (sp.). 



Fig. 7. A fragment of a frond, natural size. 



PTILOPORINA. 



(Page 507.) 

 Ptiloporina conica, Hall. 



Fig. 8. A fragment, natural size. 



Upper Helderberg group. Schoharie, JV. Y. 



Ptiloporiija sinistralis. 



Fig. 9. A frond, natural size, showing all of the secondary branches 

 proceeding from the sinistral side of the primary or larger 

 branches. 



Fig. 10. An enlargement of a portion of the same frond. x6. 

 Upper Helderberg group. Walpole, Ontario. 



Ptiloporina disparilis. 



Fig. 11. A fragment, natural size. 



Fig. 12. An enlargement from the celluliferous face, showing from two 

 to five ranges of cell apertures. x6. 

 Upper Helderberg group. Walpole, Oiitario. 



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