PLATE XLV— Continued 



Fkxk.stei.la UETUKSSA. 

 Page 111. 

 Fig. 16. An enlttig-enient fi-oni the non-celluliferous face of a frond, showing the striated branches and the 

 slender dis-sepiments, which are only about one-third the width of the branches, and very 

 much depreseed below their plane. (X t>.) 

 Fig'. 17. A portion of the celluliferous face of the same specimen, showing the comparative size and chai-- 

 acter of the bi-anches and dissepiments, and the form and arrangement of the cell apertuios. 

 (Xti.) 



Upper Helderberg group. i'W/« of the Ohio river. 



Fenestklla tenella. 



Paife 106. 

 Fig. 18. A portion of 'the non-celluliferous face of a frond, showing the chai-acter of the branches and 



<li.s.se|iiment8, their comparative size and moile of giowth. (X 6.) 

 Fig. 19. A portion of the cellulifeious face of the same specimen, sliowing the form and arrangement of the 

 cell apertujes, and the conii>aratively strong nodes along the middle of the branch. (X 6.) 

 Upper Helderberg group. I^allx of the Ohio river. 



FEXESTErXA (PoLYPOUA) CKEBK.SCENS. 

 Page 170. 

 Fig. 20. A fragment, natural size. 



Fig. 21. A portion of the non-celluliferous fare of a frond enlaiged to six diaraetere, showing the distnbu- 

 tion of nodes upon the surface. 



Upper Helderberg group. Wtatem New York. 



Fknkstella pektenlis. 



PHgo 106. 

 Fig. 22. An enlargement of a portion of the non-celluliferous face of a frond, showing the comparative 



size and character of the bi-anches and dissepiments and their mode of growth. (X 6.) 

 Fig. 23. A portion of the celluliferous fa<:e of the preceding, showing the form and arrangement of the 

 cell apertures, the occasional larger apertui-es opposite the dissepiments and the prominent 

 nodes along the middle of the branch. (X 6.) 



Upper Helderberg gi-oup. Falls of the Ohio river. 



