Thamniscus NAiius, Hall. 



Fig. 18. A portion of the celluliferous face. x6. 



Upper Helderberg group. Falls of the Ohio, 



LYROPORIDRA. 



(Page 517.) 

 Lybopobidra subquadbanp, Ulrich (sp.). 



Fig. 19. An enlargement of a portion of the celluliferous face of a 

 frond, showing the disposition of the cell apertures. 

 Lower Carboniferous. 



ANASTOMOPORA. 



(Page 517.) 

 Anastomopoba ciNCTUTA, Hall (sp.). 



Fig. 20. A fragment of a frond, natural size. 



Fig. 21. An enlargement of a portion of the noncelluliferous face, 

 showing irregular anastomosis. x6. 



Fig. 22. An enlargement of the noncelluliferous face, showing regu- 

 larly anastomosing branches. x6. 



Fig. 23. An enlargement from the celluliferous face, showing the dis- 

 position of the cell apertures and the thickened margin of 

 the frond. 

 Hamilton group. 



637 



