PLATE XLIX. 

 Fenestella pkkmaroinata. 



I'ago 127. 

 Pigs. 1, 2, 3. Enlargements from the non-cellulifei-ous face, showing the obscure characters of the branches 



and diasepiments. 

 Fig. 4. The celluliferous.face, with the carinae i-emoved, showing the arrangement of the cell apertures. 

 Fig. 5. A jwrtion of the celluliferous face of a frond. The lower half of the figure shows the carinsB 



united and with some veaiculose tissue in the lower part. 

 Fig. 6. An tmlargement from the non-celluliferoua face, showing numerous nodes ornamenting the 



branches and dissepiments. 

 Pig. 7. The base of a frond, natural size. 

 Fig. 8. A lat4!ral view of a portion of a branch, enlarged. 

 Pig. 9. A transverse section, showing the form of the bi-anches and cannse. 



Fig. 10. A section similar to the pi-ece<ling, in which the branches are largei-and the fenestrules narrower. 

 Upper Helderberg group. Falls of the Ohio river. 



Fenestella semirotunda. 



Page li&. 

 Rg. 11. The base and lower portion of a frond, natural size. 

 Fig. 12. The celluliferous face of a. fragment, natural size. 



Fig. 13. A transvei"se section of sevei-al branches, showing the elevation and expansion of the carinse. 

 Fig. 14. A transvei-se section of branches raoi-e cylindrical than the preceding. 

 Fig. 15. An enlargement of the summits of the cannse from the lower portion of the frond whei"e they are 



coimected by vesiculose tissue. 

 Fig. It). An enlargement from the non-celluliferous face, showing the involved and iri-egular branches and 



dissepiments. 

 Pig. 17. The non-celluliferous face of a specimen with moi-e i-egular fenestrules. 

 Pig. 18. An enlargement similar to the pi-eceding, but with stronger branchesand dissepiments, and smaller 



fenestrules. 

 Fig. 19. 'llie non-celluliferous side of a fragment, showing charactei-s similar to fig. 16. 

 Fig. 20. The non-celluliferous face of a specimen preserving ii'regularly distributed nodes on the branches 



and dissepiments. 

 Fig. 21. The celluliferous face with the carinse removed, showing the cell apertures. 

 Fig. 22. The celluliferous face of a specimen showing the sununits of the carinie and their iri-egular lateral 



expansions. 



Upper Helderberg group. FaUa of the Ohio river. 



