PLATE XXXVI. 



Fenkstella, sp. indet. 



Figp. . 1. A fragment, showing' the non-cellulifcrous face, natural size. 

 Pig. 2. A portion of the jii-eceding, enlarged, showing the flat thickened branches. 

 Upper Helderberg group. 



Fenestella (Polypoka) cultellata. 



Page 160. 



See Plate 41. 



Figs. 3-8. Specimens, showing different forms of the elongated supporting processes which pi-oceed from 



the frond and attach themselves to foi"eign bodies, forming an additional support to that 



afforded by the basal attachment. 

 Fig. 9. The sharjjly-stnated, spreading base of a frond attached to a valve of Atrypa retiadaris. 

 Fig. 10. An enlargement of a portion of a frond having iniusually strong branches, which ai-e anchylosed 



and solidified towai-d the margin. (X 2.) 

 Fig. 11. A portion of the frond having small fenestrules and flat branches and dissepiments. 

 Fig. 12. An enlargement of a portion of fig. 11. (X 6.) 

 Fig. 13. The non-celluliferous sidg of a portion of a fi-ond, the. branches of which have comparatively 



strong spinules. 

 Fig. 14. An enlargement of the preceding, showing more plainly the prominent oblique spinules, and 



comparative size of the branches and dissepiments. (X 6.) 

 Fig. 15. A j)ortion of the celluliferous face of a frond, natural size. 



Fig. 16. An enlargement of a portion of fig. \f>, showing the fenestrules much narrower than on the non- 

 celluliferous side, the fonn and arrangement of the cell apertures, the channeled character of 



the dissepiments and, on a portion of the figure, the central row of shai-p, elongate, cuneiform 



nodes. (X 6.) 

 Fig. 17. The celluliferous side of another specimen, natural size. 

 Fig. 18. An enlargement of a portion of fig. 17, showing the branches larger than in fig. 16 ; the cell 



apertures partially obsolete on some portions, the dissepiments not channeled, and a row of 



sharp, cuneiform elevations along the middle of each branch. (X 6.) 

 Fig. 19. A lateral \icw of one of the branches of fig. 17, to show, more distinctly, the character of the 



sharp elevations along the middle of the branch (enlarged.) 

 Fig. 20. The non-celluliferous face of a frond, natural size. 

 Pig. 21. An enlargement of a portion of fig. 20, showing more distinctly the character of the branches and 



dissepiments. 

 Fig. 22. An enlargement of another portion of the same. It differs from fig. 21, in having the fenestrules 



compai-atively nan-ower and more elongate. The upper left hand portion of the figure shows 



the pi-esence of strong lateral processes. 



Upper Helderberg group. Falls of the Ohio river. 



Fenestella quackangulakis. 



Page 158. 

 See Plates 36 and 40. 

 Fig. 38. A portion of a frond, natural size. 



Tf\g. 34. An enlargpement from the preceding, showing the angular branches and the strong nodes or 

 spinules. 



Upper Helderberg group. Folia of the Ohio riwr. 



