PLATE XLV. 

 Fenestella variapora. 



Page 104. 

 See Plate 35 



Fig. 1 . A portion of a frond near the base, natural size. 



Fig. 2. An enlargement of the preceding-, showinjr moi-e distinctly the shape of the fi-ond, the elongate 

 supporting processes near the base, the form and comparative size of the branches and dissepi- 

 ments and the aspect of the fenestrules. (X •>•) 



Fig. 3. An enlargement of a portion of the celhiliferous face of the same fr-ond, showing the form and 

 arrangement of the cell aj>erture8 and the occasional large cells immediately below the bifur- 

 cations. (X 6.) 



Fig. 4. An enlargement of another portion of the cellulifei-ous face, showing angular and carinated 

 branches. The carinse are nodose, the nodes being essentially equal in number to the cell 

 apertui-es. (X t>.) 



Fig. 5. An enlargement of the celluliferous face of a frond ; the cell apertures are obsolete, with the 

 exception of a portion of one branch. (X 6.) 



Fig. 6. An enlargement of a portion of the celluliferous face of a fi-ond ; the sui"face of the two branches 

 at the left of the figure is worn away showing the interior of the cells ; the remaining branches 

 are still more deeply weathered, the cells being entii-ely woni away and the interior of the 

 non-celluliferous ]x>rtion of the branches exjKised. (X ♦>.) 



Fig. 7. An enlargement of a portion of a non-celluliferous face of a frond, showing very irregular 

 branches, which have a width about ecjual to that of the di.s.sepinientR; the fenestrules vary in 

 foi-m from elongate-oval to circular. (X fi.) 



Fig. 8. A portion of the non-celluliferous facte of a frond, showing the branches much more regularly 

 disposed than in the preceiling figure Over the greater iKirtion of the sjiecimen the fen- 

 estrules are nearly circular. (X 6.) 



Fig. 9. An enlargement of the celluliferous face of the preceding, showing the form and arrangement of 

 the cell apertures and the prominent nodes between the ranges ; both the nodes and apertures 

 are more closely arranged than on fig. 4. (X <>.) 



Fig. 10. An enlargement of another portion of the celluliferous face of the same specimen, showing very 

 large cell aijertures occurring at iri-egular intervals, but invariably opposite a ili.ssepiment. 

 (X6.) 



Pig. 11. A lateral view of a branch, showing a transverse section of the dissepiments, the cell apertures 

 and the form of the nodes along the middle of a Itranch. (X 6.) 



Fig. 12. A lateral view of a branch (mm another fionil whei-e the nodes ai-e obsolete. The dissepiments 

 are more nearly circular in section anil more <listaiit than in fig. 11. (X tJ.) 



Fig. 13. A portion of the non-celluhferous face of a' frond encrusted by other organisms. (X 6.) 

 Up|)er Helderberg group. t\ilU of the Ohio river. 



Fenestella stbllata. 



Page 109. 

 See Plate 47. 

 Fig. 14. An enlargement of a portion of the non-celluliferous face of a frond. (X 6.) 



Fig. 15. An enlargement of a portion of the celluliferous face of the pi-eceding, showing the form and 

 arrangement of the cell apertures and the strong nodes along the middle of the branches. 

 This specimen differs very much in appearance from the usual varieties of the species, but as 

 every gratlation between the two extremes occur, there are no means of separation from the 

 typical forms. (X 6.) 



Upper Helderberg group. JPiUli of the Ohio river. 



