PLATE VI. 



UNITRYPA. 



(Page 508.) 



Unitrypa fastigata, Hall. 



Fig. 1. A fragment of a frond, showing the noncelluliferous face, 



natural size. 

 Fig. 2. A fragment of a frond, showing the unitrypic characters, 



natural size. 

 Fig. 3. A transverse section of branches and their carinse. 

 Fig. 4. A side view of a branch, showing the form, of the scalse. x6. 

 Fig. 5. An enlargement from the noncelluliferous face of the 



frond. x6. 

 Fig. 6. An enlargement, showing the summits of the carinse and their 

 connecting scalse. x6. 

 Upper Helderberg group. 



ISOTRYPA. 



(Page 510.) 



ISOTKYPA CONJUNCTIVA, Hall. 



Fig. 7. A transverse section of branches and their carinse. x6. 

 Fig. 8. A side view of a portion of a branch and its carina. x6. 

 Fig. 9. A side view of the upper portion of a branch, showing the 



colurnellar appearance of the broken carinae; in this respect 



closely resembling a Hemitetpa. 

 Fig. 10. An enlargement from the noncelluliferous face of a frond, 



showing the conspicuous pores on or near the dissepiments. 

 Fig. 11. An enlargement from the celluliferous face of a frond. x6. 

 Fig. 12, An enlargement, showing the summits of the carinse and their 



connecting bars. x6. 

 Upper Helderberg group. Wal2:)ole, Ontario . 



TECTULIPORELLA. 



(Page 510.) 

 Tectulipoeella consimilis. Hall (sp.). 

 Fig. 13. An enlargement. The left-hand portion of the figure shows 

 the summits of the carinse and connecting bars; the central, 

 the celluliferous face of the branches; the right-hand 

 portion the interior of the branches. x6. 

 Fig. 14. An enlargement, showing the celluliferous face of the 



branches. x6. 

 Fig. 15. An enlargement, showing the summits of the carinse and 

 their connecting bars. x6. 

 Upper Helderberg group. 



630 



