PLATE XXII. 

 Fenestella (Uni'irypa) Nervia. 



Page 55. 

 Fig. 1. The celluliferous face of a funnel-shaped frond. 



Lower Helderberg group. Clarksville, N. T. .! .VJ. 



Fig. 2. An enlargement of the preceding, sho\\'ing the cell apertures, with a portion of the surface ex- 

 foliated, disclosing the interior structure, cell walls, etc. 

 Fig. 3. An enlargement from the celluliferous face of specimen fig. 1, where the carinal crests are ex- 

 tended into lateral bars, meeting those from the opposite side. 

 Fig. 6. An enlargement from the celluliferous face of another specimen. 



Fig'. 9. A fragment ; natural size, showing the extension of the lateral bai-s connecting the intercellular 

 carime. 



Lower Helderberg group. Olarksville, iV. T. 

 Vig. 10. An enlargement of the preceding. 



Fenestella (Polypora) compacta. 



Page 63. 

 See Plate 18. 



Fig. 4. The non-ceUuliferous face of a fragment. .-,, 



Fig. 5. An enlargement from the preceding. 



Lower Helderberg gi-oup. Clarksville, N. Y. 



Fenestella adormata. 



Page «,. ,.^^^^ 



Fig. 7. An enlargement of the non-ceUuliferous face. """^^ : 



Lower Heldei-berg group. Clarksville, N. V. 

 Fig. 8. An enlargement of the ceUuliferous face of the preceding. 



Fenestella (Uxitrypa) Nervia, van constricta. 



Page 66. 

 Fig. 11. An enlargement of the non-cellulifei-ous face, showing the thickened gi-anulated branches and small 



fenesti-ules. 

 Fig. 12. An enlargement from the celluliferous face of the preceding specimen, showing the thickened 



inter-cellular crests and connecting bars on a pai*! of the surface. 



j 



Fenestella (Hemitrypa) biserialis. 



Page 57. 

 Fig. 13. The base of the celluliferous side of a funnel-shaped frond, natural size. 

 Fig. 16. An enlargement of the non-ceUuliferous face of another specimen. 

 Fig. 17. An enlargement of the celluliferous face from the specimen tig. 13, where the elevated crests of 



the intercellular cariua! are broken off showing the cell-ajjertures. 

 Fig. 18. An enlargement from the celluliferous side of specimen tig. 13, preserving the elevated crests of 

 the carinae, and the lateral processes uniting in a longitudinal bar. 

 Lower Helderberg gi-oup, ^ear Clarksville, N. Y, 



Fenestella (Hemitrypa) biseralis, var. exilis. 



Page 57. 

 Vig. 14. A sectional view enlarged, sljowing the elevation of the interceUular crests and the connecting 



processes. (X 4.) 

 Fig. 15. An enlargement from the nou-celluliferous face of a specimen. 

 Lower Helderberg group. Near Clarksville, N. Y. 



