PLATE XXX. 
Fig. 1. 
Fig. 2. 
Fig. 3. 
Fig. 4. 
Fig. 5. 
Fig. 6. 
Fig. 7. 
Fig. 8. 
Fig. 9. 
Fig. 10. 
Fig. 11. 
Fig. 12. 
Fig. 13. 
Fig. 14. 
Fig. 15. 
Fig. 16. 
Fig. 17. 
Fig. 18. 
Fig. 19. 
Fig. 20. 
Lichenalia substellata. 
Page 7S. 
See Plate 26. 
A specimen, natural size, having elevated maculae. 
A specimen, showing the general aspect of the species, the form and arrangement of the maculae, 
and the large cellules immediately surrounding them. 
One of the maculae, showing the contiguous cell apertures. (X 16.) 
A portion of the surface, showing the cell apertures closed by opercula. (X 16.) 
Another portion, showing the cell apertures. (X 16.) 
An enlargement of the oblique cell apertures, with a portion of the cell tubes exposed. (X 16.) 
A portion of a frond, where the surface has been worn away, showing the interstitial pits. (X 16.) 
A portion of the surface, showing cell apertures with elevated margins and obscure denticulations. 
(X 16.) 
A vertical section, showing cell tubes and septate intercellular tubules. 
A vertical section from another frond, showing the cell tubes more closely arranged than in the 
preceding. 
A portion of the surface, showing- some of the cell apertures, closed and presenting a pustuliform 
aspect. (X 16.) 
Upper Helderberg group. Falls of the Ohio river. 
Lichenalia (Pileotrypa) denticulata. 
Page SL 
See Plate 26. 
A specimen, natural size, showing the general appearance of the species, the form and arrange¬ 
ment of the maculae etc. 
A portion of the surface of the preceding, showing the form and arrangement of the cell apertures. 
(X 6.) 
An oblique view of a portion of the surface, showing the height and form of the elevated cell 
margins. (X 6.) 
Two views, each one of a single cell aperture seen obliquely from above, and greatly enlarged, 
showing more distinctly the appearance of the elevated cell margins. The figure has been 
inadvertently shaded between the cells which should be represented as two distinct figures. 
Front and lateral views of the elevated cell margins. (X 16.) 
A portion of the surface of a frond, showing- the form and arrangement of the cells and the denti¬ 
culated cell margins. (X 16.) 
Three cell apertures much enlarged, to show the variation in their form and margins. 
A vertical section of a portion of a frond, showing oblique cell tubes. 
A vertical section from another frond, showing the cell tubes and intercellular vesicular structure. 
Upper Helderberg group. Falls of the Ohio river. 
