PLATE LXVI. 



Clonopora fasciculata. 



Psge289. 

 Fig. 1. An enlargement, showing the form of the cell tubes and their manner of growth. (X 6.) 



Upper Helderberg group. Onmidaga Valley, N. T. 

 Fig. 2. An enlargement from another specimen having somewhat larger cell tubes than the preceding- 

 (X 6.) ^' 



Upper Helderberg group. Onondaga Valley, N. T. 



Clonopoka semireductus. 



rage 389. 

 Fig. 3. A fragment, natural size. 



Fig. 4. An enlargement from the preceding, showing more distinctly the form of the cell tubes and their 

 moiie of growth. (X 6.) 



Upper Helderberg group. Patlx of the Ohio river. 



Clonopora incurva. 



Page 289. 

 Fig. 5. A fragment of a frond, natural size. 



Fig. 6. An enlargement of the preceding, showing more distinctly the form of the cell tubes and their 

 spiral mode of growth. (X S.) 



Cystopora GENICULATA. 



Page 103. 

 Fig. 7. A fragment, natural size. 



Fig. 8. An enlargement, showing the ampuUiform cell tubes and the constricted apertures. (X 6.) 



Fig. 9. An enlargement from a specimen having the outer portion of the cell tubes broken away. (X 6.) 



Fig. 10. An enlargement, showing more distinctly the characters illustrated in figure 8. 



Upper Helderberg group. liblls of the Ohio river. 



Thamniscus nanus. 



Page 293. 

 Fig. II. A fragment, natural size. 



Fig. 12. An enlargement of the non-celluliferous face of a frond. (X 6.) 



Fig. 13. An enlargement fi-om the celluliferous face, showing the form and disposition of the cell aper- 



tui-es. (X 6.) 



Upper Helderberg group, fhlls of the Ohio river. 



Bactkopoka curvata. 



Page 194. 

 Fig. 14. A fragment, natural size. 



Fig. 15. An enlargement from the preceding, showing the obtusely pointed base, the form and disposition 



of the cell apertures and the Hdges separating them. (X *)■) 



Fig. 16. A still farther enlargement, showing more distinctly the charactei-s of the cell apertures. (X 18.) 



Hamilton group. Fall-brook, near Canandaigua lake, N. Y. 



Nemataxis simplex. 



Page 193. 

 Fig. 17. A fragment, natural size. 



Fig. 18. An enlargement of the preceding, showing the form and disposition of the cell apertures. (X 6.) 

 Fig. 19. An enlargement of a natural section, showing the foi-m and manner of growth of the cell tubes. 

 (X 6.) 



Hamilton group. Darien Centre, N. Y. 



