PLATE XXXY. 
Fig-. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fenestella (Polypora) celsipora, var. minima. 
Page 151. 
See Plate 41. 
1. The base and lower portion of a frond, natural size. 
2. A portion of the non-celluliferous face of a frond. (X 6.) 
3. A portion of the celluliferous face of a frond, enlarged, showing the fenestrules narrower than on 
the non-celluliferous side, and the form and arrangement of the cell apertures. (X 6.) 
4. A portion of one of the branches of fig. 3, enlarged, showing the form of cell apertures and mar¬ 
ginal radiating lines, which are probably caused by weathering. (X 18.) 
Upper Ilelderberg group. Falls of the Ohio river. 
Fenestella (Polypora) aculeata. 
Page 157. 
See Plate 40. 
5. A specimen, natural size, showing the spreading striated base and lower portion of the frond. 
6. An enlargement of the non-celluliferous face of the preceding, showing the form and nodose 
character of the branches. 
7. An enlargement of the celluliferous face of the same, showing the comparative size of the 
branches and dissepiments, the form and arrangement of cell apertures and the numerous 
spinules. 
Upper Ilelderberg group. Falls of the Ohio river. 
Fenestella (Polypora) quadrangularis. 
Page 158. 
See Plates 36 and 40. 
8. The non-celluliferous face of a specimen, natural size. 
9. A portion of the celluliferous face of the preceding, enlarged, showing the comparative size of 
branches and fenestrules, the form and arrangement of cell apertures. (X 6.) 
10. A portion of the non-celluliferous side of the same, enlarg-ed, showing comparative size of the 
branches and dissepiments, the carination of the branches and the less distinct carination of 
the dissepiments. 
11. An enlargement of one side of a branch, to show the form of the spines of the non-celluliferous 
face of the branches. 
12. A specimen, natural size, showing the base and lower portion of the frond, with numerous 
processes attached to, and growing upon a frond of Fenestella ( Unitrypa) stipata. 
13. A portion of the celluliferous face of fig. 12, enlarged, showing the form and arrangement of the 
cell apertures and the prominent, irregular nodes. (X 6.) 
Upper Helderberg group. Falls of the Ohio river. 
Fenestella (Polypora) labvistriata, n. sp. 
Page 159. 
14. A portion of the non-celluliferous face of a frond, natural size. 
15. An enlargement of a portion of the non-celluliferous side of fig. 14, showing the comparative 
size of the branches and dissepiments, and the angular and spinulose branches. 
16. An enlargement of a portion of the celluliferous face of fig. 14, showing the character of branches 
and dissepiments and the form and arrangement of the cell apertures. 
Upper Helderberg group. Falls of the Ohio river. 
Fenestella, sp. indet. 
17. A specimen, showing the bases of several fronds, growing- upon an overthrown individual of the 
same or another species. 
18. A specimen, showing the concentric aggregation of the substance as produced during the process 
of silification. 
Upper Helderberg group. 
