PLATE XLI—Continued. 
FeNESTELLA (POLYPOEA) CELS1PORA. 
Page 150. 
See Plate 42. 
Fig. 16. A portion of the celluliferous face of a frond, showing the comparative size and character of the 
branches and dissepiments, the form and arrangement of the cell apertures and the ridges 
separating them. (X 6.) 
Fig. 17. An enlargement from a gutta percha cast of the impression of the celluliferous face, where the 
tissue has been removed. (X 6.) 
Fig. 18. The non-celluliferous face of a frond. The branch at the left is worn so that it presents a flattened 
appearance, filiform tissue, and the other branches are still more worn and the surface entirely 
removed, showing the fibrous condition of the solid portion of the branch. (X 6.) 
Fig. 19. A portion of the celluliferous face. The branch on the right side of the figure shows the cell 
apertures in a perfect condition ; the remaining branches have the surface macerated and the 
cells filled with solid matter, making them more prominent. (X 6.) 
Fig. 20. A portion of the non-celluliferous face of a frond, showing considerable valuation in the size and 
form of the fenestrules. (X 6.) 
Fig. 21. A portion of a specimen, in which the branches are more slender than in the preceding ; the 
fenestrules are quadrangular and frequently twice the width of the branches. (X 6.) 
Fig. 22. A portion of the celluliferous face of a frond, showing the longitudinal rows of cell apertures, the 
elevation of the central row, the narrow fenestrules and angular dissepiments. (X 6.) 
Upper Helderberg group. Ontario, Canada. 
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