PLATE XIX. 
Fenestella (Polypora) stricta. 
Page 59. 
Fig-. 1. A fragment of a frond, natural size. 
Lower Helderberg group. Clarksville, JSf. Y. 
Fig. 2. An enlargement of the non-celluliferous face of the preceding. 
Fenestella (Polypora) Eudora. 
Page 58. 
Fig. 3. A fragment of the non-celluliferous face of a frond, natural size. 
Fig. 4. An enlargement of the preceding. 
Fig. 5. An enlargement of the celluliferous face of a frond, referred to this species with doubt. 
Lower Helderberg group. Clarksville, N. Y. 
Fig. 6. A fragment of the non-celluliferous face of the frond. 
Fig. 7. An enlargement of the celluliferous face of the preceding, showing smaller cell apertures, which 
are in some parts more numerous. 
Lower Helderberg group. Clarksville, _ZV. Y. 
Fig. 8. A fragment of the non-celluliferous face of a specimen. 
Fig. 9. An enlargement from the celluliferous face of the preceding, showing more elongate fenestrules 
than the above forms. 
Fig. 10. An enlargement of the non-celluliferous face of the specimen tig. S. 
Fenestella tEsyle. 
Page 46. 
Fig. 11. A portion of the frond, natural size, showing the non-celluliferous face. 
Fig. 12. An enlargement of the non-celluliferous face, from the preceding. 
Lower Helderberg group. JSfew Salem, N. Y. 
Fig. 13. An enlargement of the non-celluliferous face of another specimen, showing more slender branches 
and wider fenestrules. 
Fenestella (Polypora) Idothea. 
Fig. 14. A portion of a frond, natural size, showing the celluliferous face. 
Lower Helderberg group. Clarksville, N. Y. 
Fig. 15. An enlargement from the preceding. 
Fenestella Spio. 
Page 47. 
Fig. 16. A portion of the celluliferous face of a frond, enlarged. 
Lower Helderberg group. Clarksville, N. Y. 
Fenestella Althaea. 
Page 48. 
Fig. 17. An enlargement of the non-celluliferous face of two fragments a and b, which are probably parts 
of the same frond. 
Lower Helderberg group. Clarksville, N. Y. 
Fig. 18. An enlargement of the non-celluliferous face of another specimen, showing larger fenestrules. 
Lower Helderberg group. Clarksville, N. Y. 
Fig. 19. An enlargement of the non-celluliferous face of a fragment from another frond. 
Lower Helderberg group. Clarksville, N. Y. 
