PLATE XXXYI. 
Fenestella, sp. indet. 
Fig. , 1. A fragment, showing the non-celluliferous face, natural size. 
Fig. 2. A portion of the preceding, enlarged, showing the flat thickened branches. 
Upper Helderberg group. 
Figs. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fenestella (Polypora) cultellata. 
Page 160. 
See Plate 41. 
3-8. Specimens, showing different forms of the elongated supporting processes which proceed from 
the frond and attach themselves to foreign bodies, forming an additional support to that 
afforded by the basal attachment. 
9. The sharply-striated, spreading base of a frond attached to a valve of Af rypa reticularis. 
10. An enlargement of a portion of a frond having unusually strong branches, which are anchylosed 
and solidified toward the margin. (X 2.) 
11. A portion of the frond having small fenestrules and flat branches and dissepiments. 
12. An enlargement of a portion of fig. 11. (X 6.) 
13. The non-celluliferous side of a portion of a frond, the branches of which have comparatively 
strong spinules. 
14. An enlargement of the preceding, showing more plainly the prominent oblique spinules, and 
comparative size of the branches and dissepiments. (X 6.) 
15. A portion of the celluliferous face of a frond, natural size. 
16. An enlargement of a portion of fig. 15, showing the fenestrules much narrower than on the non- 
celluliferous side, the form and arrang-ement of the cell apertures, the channeled character of 
the dissepiments and, on a portion of the figure, the central row of sharp, elongate, cuneiform 
nodes. (X 6.) 
17. The celluliferous side of another specimen, natural size. 
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.) 
19. A lateral view 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.) 
20. The non-celluliferous face of a frond, natural size. 
21. An enlargement of a portion of fig. 20, showing more distinctly the character of the branches and 
dissepiments. 
22. An enlargement of another portion of the same. It differs from fig. 21, in having the fenestrules 
comparatively narrower and more elongate. The upper left hand portion of the figure shows 
the presence of strong lateral processes. 
Upper Helderberg group. Falls of the Ohio m>er. 
Fenestella quadrangularis. 
Page 158. 
See Plates 35 and 40. 
Fig. 23. A portion of a frond, natural size. 
Fig. 24. An enlargement from the preceding, showing the angular branches and the strong nodes or 
spinules. 
Upper Helderberg group. Falls of the Ohio river. 
