PLATE XXXI. 
Lichenalia lunata. 
Page 77. 
Fig-. 1. The upper surface of a specimen, natural size. 
Fig. 2. An enlargement of the surface to show the arrangement of the cell apertures. (X 6.) 
Fig. 3. A specimen in which the surface has been removed, showing the intercellular structure. (X 6.) 
Fig. 4. A vertical section, showing the septate cell tubes, the striations left by the denticulations of the 
aperture in its advancing growth, and the intermediate septate tubuli. (X 6.) 
Fig. 5. A vertical section, showing the irregular vesicular structure of the intercellular tissue. (X 6.) 
Fig. 6. A vertical section, showing the striation of the cell walls and a solid intercellular space. (X ti.) 
Fig. 7. A portion of the surface, enlarged, showing the cell apertures and denticulations. (X 18.) 
Fig. 8. A single cell aperture, enlarged to 40 diameters. 
Fig. 9. A portion of an abraded surface, showing the character of the intercellular tissue. 
Upper Helderberg group. Falls of the Ohio river. 
Lichenalia conulata. 
Page 81. 
Fig. 10 A fragment of a specimen, natural size. 
Fig. 11. A portion of the surface enlarged, showing an inflated pustuliform condition. (X 10.) 
Fig. 12. An enlargement of the surface from the center of a monticule, showing the cell apertures 
projected on the exterior in the form of inflated oviform expansions with contracted aper¬ 
tures. (X 18.) 
Fig. 13. An enlargement of an abraded surface, showing the intercellular tissue. (X 18.) 
Fig. 14. A vertical section, showing an irregular vesiculose structure near the base, becoming more 
regular above. 
Upper Helderberg group. Falls of the Ohio river. 
Lichenalia? (Glossotrypa) paliformis. 
Page 85 
Fig. 15. A fragment of a tubular branch or frond, natural size. 
Fig. 16. An enlargement of the preceding, showing the arrangement of the cell apertures. (X 6.) 
Fig. 17. An enlargement of a portion of the surface. (X IS.) 
Fig. 18. A section of the tubular frond, showing the cells with indications of intercellular tissue. (X 6.) 
Upper Helderberg group. Falls of the Ohio river. 
Lichenalia (Selenopora) complexa. 
Page 87. 
Fig. 19. A portion of the natural surface enlarged, showing the character of the cell apertures with their 
vestibular areas. (X 6.) 
Fig. 10. The surface of another specimen, showing larger apertures and surrounding areas than the pre¬ 
ceding. (X 6.) 
Upper Helderberg group. Falls of the Ohio river. 
Lichenalia (Pileotrypa) pyriformis. 
Page 82. 
Fig. 21. A fragment, natural size. 
Fig. 22. A portion of the surface where the cell openings have strongly elevated and denticulated 
posterior margins. (X IS.) The anterior margins of the apertures, as represented in the 
figure, are too prominent. 
Fig. 23. A vertical section, showing the intermediate vesicular structure which has marked the exterior 
of the cell walls. (X 6.) 
