PLATE XX. 

 Fenestella crebripoka. 



Pufro 43. 

 A fi-agment of the celluliferous face of a frond, natural size. 

 An enlargement of the noncelluliferous face of a frag^ment. 

 An enlargement of the celluliferous face of specimen fig. 1. 

 Lower Helderberg group. CtarksvUle, N. T. 



Fenestella Sylvia. 



Page «. 

 Figr. 4. A fragment of the non-celluliferous face of a frond, natural size. 

 Pijf. 5. An enlarg'ement of the non-celluliferous face of the preceding'. 



Pig. 6. An enlargement from the non-cell uliferous face of specimen fig. 4, showing the fomi of fenestrules, 

 and from three to five lines or striffi on each of the branches, contrasting with fig. 5, from another 

 part of the same frond. 

 Rg. 7. An enlargement of the celluliferous face from another specimen. 

 Lower Helderberg group. Near Clarksville, N. T. 



Fenestella, sp. ? 

 Fig. 8. The non-celluliferous face, worn in such a manner as to show the base of the cellules. 



Fenkstella Philia. 



Page 50. 

 Pig. 9. A fragment of the non-celluliferous face, natural size. 

 Pig. 10. An enlargement from the pi-eceding. 

 Kg. 11. An enlargement of the celluliferous face. 



Lower Helderberg group. New iSalem, Albany Co., N. Y. 



Fenestella Hestia. 



Page 4S. 

 Pig. 12. A fragment of the non-celluliferous face. 



Pig. 13. An enlargement of a portion of the preceding, showing pustules and the strongly striated surface 

 of the branches. 



Lower Helderberg group. Schoharie, N. T. 



Fenestella Cleia. 



Page 45. 

 Pig. 14. An enlargement from the non-celluliferous face of a frond. 

 Pig. 15. An enlargfement of the celluliferous face. 



Lower Helderberg group. Near Clarksville, N. Y. 



Fenestella junceus. 



Page 44. 

 Pig. 16. A fragment of the celluliferous face, natural size. 

 Pig. 17. An enlargement of the non-cellulifei-oua 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. 

 Pig. 19. An enlargement from the celluliferous face of a frond. 

 Pig. 20. A fragment of the non-celluliferous face of a frond, natural size. 

 Pig. 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. 



