PLATE XXXIV. 



Fenestella (Polypora) rigida. 



I'agc 155. 

 Fig. 1. A specimen, natural size. 



Fig. 2. An enlai-geiuent of a poi'tion of tig. 1, showing' the appearance of the non-celluliferous side. 

 Fig. 3. An enlargement of a portion of the celluliferous side of a specimen, showing the form and 

 ari-angement of the cell apertures, and the longitudinal ridges dividing the ranges of cell 

 apertures. (X 6.) 



Upper Helderberg gi-oup. Near Thinnpson's lake, Albany eowUy, N. Y. 



Fenestella (Polypora) robusta. 



Page IM. 

 See Plates 37, 39 and 4ti. 

 Fig. 4. A portion of the non-celluliferoua aide of a frond, natural size. 

 Fig. 5. A portion of the celluliferous side of a fi-ond, enlarged, showing the form and arrangement of 



cell apertures, and comparative size of branches and dissepiments. (X 6.) 

 Fig. 6. An enlargement of a portion of the celluliferous side of a frond ; the greater portion of th« exterior 



of the branches is broken away, showing the bases of the polygonal cells. (X 6.) 

 Fig. 7. An enlargement of the non-celluliferous side of a specimen, showing the form and compai-ative size 

 of branches and dissepiments : the branches of this speoimen are narrower than those of the 

 frond fi*om which tigs. 5 and (5 were made. (X <i.) 



Upper Helderberg group. IValpole, Canada. 



Fenestella (Polypora) largissima. 



Page 160. 

 Fig. 8. The BOn-celluliferous side of a frond, natural size. 



Fig. 9. An enlargement of a portion of tig. 8, showing the form and comparative size of the non-celluliferous 

 face of branches and dissepiments. (X 6.) 



Upper Helderberg group. Central New York. 



Fenestella propria. 



Page 157. 

 Fig. 10. A portion of the non-celluliferous face of a frond, natural size. 

 Fig. 11. An enlargement of a portion of fig. 10, showing the character of the non-celluliferous face of a 



frond. (X 6.) 

 Fig. 12. An enlargement of an impression of the non-celluliferous face of a frond. tX 6.) 

 Fig. 13. An enlargement of a portion of the celluliferous face of a fi-ond, showing the form and aii-ange- 

 ment of cell apertures and the carinaled dissepiments. (X B.) 

 Upper Helderberg group. Near Buffalo, N. Y. 



