PLATE XLIII. 
Fenestella (Polypora) robusta. 
Page 156. 
See Plates 34, 37, 39 and 46. 
Fig'. 1. An enlargement of a portion of the celluliferous face, showing the rows of cell apertures separated 
by narrow ridges. (X 6.) 
Upper Helderberg group. Walpole, Ontario, Canada. 
Fenestella (Ptiloporina) conica. 
Page 172. 
Fig. 2. A nearly entire frond, natural size. 
Figs. 3, 4. Enlargements from the preceding, showing the primary and secondary branches. 
Upper Helderberg- group. Schoharie, N. Y. 
Fenestella (Ptiloporina) pinnata. 
Page 172. 
Fig. 5. A portion of a frond, natural size. 
Fig. 6. An enlargement from the preceding, showing the striated branches and dissepiments. 
Upper Helderberg group. Schoharie, N. Y. 
Fenestella (Ptiloporina) disparilis. 
Page 173. 
Fig. 7. An enlargement of the non-celluliferous face of a fi*ond. (X 6.) 
Fig. 8. An enlargement from a decorticated specimen, showing- the arrangement of the cells on the 
interior of the branches. (X 6.) 
Upper Helderberg group. Walpole, Ontario, Canada. 
Fenestella (Ptiloporina) sinistralis. 
Page 174. 
Fig. 9. The non-celluliferous face of a large portion of a frond, natural size, showing the disposition of 
the primary and secondary branches. 
Schoharie grit. Schoharie, N. Y. 
Fenestella (Polypora) rustica. 
Page 169. 
Fig. 10. A portion of the non-celluliferous face of a frond, natural size. 
Fig. 11. An enlargement from the preceding. (X 6.) 
Fig. 12. An enlargement of the celluliferous face, showing a weathered condition of the specimen. (X 6.) 
Fig. 13. An enlargement showing the characters of the celluliforous face of the frond. (X 6.) 
Upper Helderberg group. Walpole, Ontario, Canada. 
