I 



PLATE V. 



HEMITRYPA. 



(Page 507.) 

 Hemiteypa ceibrosa, Hall. 

 Fig. 1. An enlargement of the base of a specimen. x6. 

 Fig. 2. A still further enlargement of the same specimen. xl8. 

 Upper Helderberg group. Falls of the Ohio . 



Hemitrtpa columellata, Hall. I 



Fig. 3. A fragment, natural size. 



Fig. 4. An enlargement from the noncelluliferons face of the 



frond. x6. 

 Fig. 5. An enlargement from the celluliferous face of a frond. The 



upper portion of the figure shows the superimposed hemi- 



trypic structure. x6. 

 Fig. 6. A side view of a portion of a branch and carina. x6 . 

 Fig. Y. End view of branches and carinae. x6. 

 Fig. 8. Side view of a branch showing the cell apertures and the 



columellar appearance of the broken carina. 

 Fig. 9. Noncelluliferons face. x6. 



Fig. 10. An impression in the rock of the celluliferous face. x6. 

 Fig. 11. Pseudo-carinse and connecting scalse. x6. 



Upper Helderberg group. Walpole^ Ontario. 



UNITRYPA. 



(Page 508.) 

 Unitetpa connexa, Hall. 



Fig. 12. An enlargement of the summits of the carinae and connecting 

 gcalse. On portions of the figure the scalae are of unitrypic 

 character, while on other portions they are hemitrypic. 

 This species could, with equal propriety, be included in 

 either Unitrtpa or Hemiteypa. 



Fig. 13. Side view of a portion of a branch and its carinse. x6. 



Fig. 14. Transverse section of branches and carinae. x6 . 

 Upper Helderberg group. 



