PLATE XXXI. 



LlCHENALIA I.UNATA. 

 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 remi)vo<i, showing the intercellular structure. (X 6.) 

 Fig. 4. A vertical section, showing the septate cell tabes, the striations left by the denticulations of the 

 ; -. II aperture in its ailvancing 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 ami a solid intercellular space. (X t>.) 

 Fig. 7. A portion of the sui-face, enlai-ged, showing the cell apertures »nd denticulations. (X 18.) 

 Fig. 8. A single cell aperture, enlarged to 40 diameters^ i / i,i/ /.ni )iil 

 Fig. 9. A portion of an abraded surface, showing the character of the intercellular tissue. 

 Upper Helderberg group. FaUt of the Ohio river. 



LlCHENALIA CONULATA. 

 Page 81. 

 Fig. 10 A fragment of a specimen, natui-al .size. 



Pig. 11. A portion of the surface enlai-ged, showing an inflated puetaliform condition. (X 10.) 

 Fig. 12. An enlargement of the surface from the center of a monticule, showing the cell apertui-es 

 pi-ojected on the exterior in the form of inflated oviform expansiona with contracted aper- 

 tures. (X 18.) 

 Fig. 13. An enlargement of an abraded sui-face, showing the intercellular tissue. (X 18.) 

 Fig. 14. A vertical section, showing an in-egular vesiculose structure near the baae, becoming more 

 regular above. 



Upper Helderberg group. PaUa of the Ohio river. 



LlCHENALFA? (GlOSSOTKYPA) PALIFORMI.S. 

 Fag« «6 

 Fig. 15. A fragment of a tubular branch or frond, natural size. 



Fig. 16. An enlargement of the preceding, showing the ai-rangement of the cell apertures. (X 6.) 

 Fig. 17. An enlargement of a jwrt ion of the 8urfai:e. (X 18.) 



Fig. 18. A section of the tubular frond, showing the cells with indications of intarcellalsr tisBue. (X 6.) 

 Dpper Helderberg group. FaiU of the Ohio river. ■iMaU ■I'l-ci i 



LiCHENAUA (SeLENOPORA) COMPLEXA. 



Page KT. 



Fig. 19. A portion of the natural surface enlarged, showing the character of the cell apertures with their 



ve.itiliiilar ai'eas. (X 6.) 

 Fig. -0. The surface of another specimen, showing larger apertures and surrounding areas than the prsj- 



ceding. (X 6.) 



;^ .'r.tu-uy> • 



Upper Helderberg group. Falh of the Ohio river. 



LlCHENALIA (PiLEOTRYPA) PYKIFORMIS. 



Paife 82. 

 Fig. 21. A fragment, natural size. 



Fig. 22. A portion of the surface whei-e the cell openings have strongly elevated and denticutated 

 posterior margins. (X 18.) The anterior margins of the apertures, ae represented iri'tlie 

 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.) 



