PLATE LXYI. 
Clonopora fasciculata. 
Page 289. 
Fig-. 1. An enlargement, showing the form of the cell tubes and their manner of growth. (X 6.) 
Upper Helderberg group. Onondaga Valley, N. Y. 
Fig. 2. An enlargement from another specimen having somewhat larger cell tubes than the preceding. 
(X 6.) 
Upper Helderberg group. Onondaga Valley, N. Y. 
Clonopora semireductus. 
Page 289. 
Fig. 3. A fragment, natural size. 
Fig. 4. An enlargement from the preceding, showing more distinctly the form of the cell tubes and their 
mode of growth. (X 6.) 
Upper Helderberg group. Falls 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 6.) 
Cystopora geniculata. 
„ Page 103. 
Fig. 7. A fragment, natural size. 
Fig. 8. An enlargement, showing the ampulliform 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. Falls of the Ohio river. 
Thamniscus NANUS. 
Page 292. 
Fig. 11. A fragment, natural size. 
Fig. 12. An enlargement of the non-celluliferous face of a frond. (X S.) 
Fig. 13. An enlargement from the celluliferous face, showing the form and disposition of the cell aper¬ 
tures. (X 6.) 
Upper Helderberg- group. Falls of the Ohio river. 
Bactropora curvata. 
Page 191. 
A fragment, natural size. 
An enlargement from the preceding, showing the obtusely pointed base, the form and disposition 
of the cell apertures and the ridges separating them. (X 6.) 
A still farther enlargement, showing more distinctly the characters 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 form and manner of growth of the cell tubes. 
(X 6.) 
Hamilton group. Darien Centre, N. Y. 
Fig. 14. 
Fig. 15. 
Fig. 16. 
