PLATE XX. 
Fenestella crebripora. 
Page 43. 
Fig. 1. A fragment of the celluliferous face of a frond, natural size. 
Fig. 2. An enlargement of the non-celluliferous face of a fragment. 
Fig. 3. An enlargement of the celluliferous face of specimen fig. 1. 
Lower Helderherg group. Clarksville, N. Y. 
Fenestella Sylvia. 
Page 49. 
A fragment of the non-celluliferous face of a frond, natural size. 
An enlargement of the non-celluliferous face of the preceding. 
An enlargement from the non-celluliferous face of specimen fig. 4, showing the form of fenestrules, 
and from three to five lines or striae on each of the branches, contrasting with fig. 5, from another 
part of the same frond. 
An enlargement of the celluliferous face from another specimen. 
Lower Helderherg group. Near Clarksville, N. Y. 
Fenestella, sp. ? 
Fig. 8. The non-celluliferous face, worn in such a manner as to show the base of the cellules. 
Fenestella Philia. 
Page 50. 
Fig. 9. A fragment of the non-celluliferous face, natural size. 
Fig. 10. An enlargement from the preceding. 
Fig. 11. An enlargement of the celluliferous face. 
Lower Helderberg group. New Salem, Albany Co., N. Y. 
Fenestella Hestia. 
Page 45. 
Fig. 12. A fragment of the non-celluliferous face. 
Fig. 13. An enlargement of a portion of the preceding, showing pust.ules and the strongly striated surface 
of the branches. 
Lower Helderberg group. Schoharie, N. Y. 
Fenestella Cleia. 
Page 45. 
Fig. 14. An enlargement from the non-celluliferous face of a frond. 
Fig. 15. An enlargement of the celluliferous face. 
Lower Helderberg group. Near Clarksville, N. Y. 
Fenestella junceus. 
Page 44. 
Fig. 16. A fragment of the celluliferous face, natural size. 
Fig. 17. An enlargement of the non-celluliferous face of the frond. 
Fig. 18. An enlargement of the celluliferous face from the specimen fig. 16. 
Lower Helderberg group. Near Clarksville, N. Y. 
Fenestella Adraste. 
Page 48. 
Fig. 19. An enlargement from the celluliferous face of a frond. 
Fig. 20. A fragment of the non-celluliferous face of a frond, natural size. 
Fig. 21. An enlargement from the preceding. 
Fig. 22. An enlargement of the celluliferous face of a frond, with an outline section of a branch at the right 
hand side of the figure. 
Lower Helderberg group. Near Clarksville, N. Y. 
Fig. 4. 
Fig. 5. 
Fig. 6. 
Fig. 7. 
