PLATK XLII— ContlnncU. 



Fknestella (Poltpora) L.EVINODATA. 



Pago 169. 



Fig. 12. A fragment of the non-celluliferoiis face of a fi-ond, natural size. 



Fig. 13. An enlargement of a portion of tiff. 12. The brancho.'s are angular, sometimes carinated, very 

 irregular and with comparativi'ly strong, iri-egulni-ly disposed nodes. (X B.) 



Fig. 14. An enlargement of another portion of fig. 12. 'ITie branches are regular ; branches ami dissepi- 

 ments angular and carinated, with minute nodes on the carination of the branch opi)Osite the 

 dissepiments. (X H.) 



Fig. 15. An enlargement from the celluliferous face of a frond. The surface of the branch at the right is 

 remove<l, showing the cellular interior and the form and arrangement of the cells. The con- 

 tiguous branch has the surface partially worn away, showing the apertures of the ccsUs very 

 much enlarged, and but partially retaining their circular form The remaining branches ai-e 

 in a perfect condition and show the form and ari-angement of the cell apertures, the granules 

 between the apertui-es, and, on the branch at the left, the comparatively strong ridges sepa- 

 rating the longitudinal i-anges of cell apertures. (X 6.) 



Upper Helderberg g^oup. FWls of the Ohio river. 



Fknestella BISERIATA. 



Page 11 J. 

 Fig. 16. A fragment of the non-celluliferous face of a frond, natural size. 

 Fig. 17. An enlargement of a portion of tig. 16, showing the comparative size and character of the branches 



and dissepiments, and the fonn of the fenestrules. (X t>.) 

 Fig. 18. An enlargement from the celluliferous face of a frond ; the branches and dissepiments are angular 

 and carinated ; the cell apertures in two ranges. (X 6.) 

 Upjier Helderberg group. Cherry Valley, iV. Y. 



Fbnestella PEOULIARIS. 

 Pace 113. 

 Fig. 19. A fragment of the non-celluliferous face of a specimen, natural size. 

 Fig. 30. An enlargement of a jiortion of fig. 19. The sui-fiu;e has been macerated and the external 



markings are obsolete, the branches appearing flat. (X *>■) 

 Fig. 21. An enlargement of another portion of fig. 19. The upper portion is well preserved, showing the 

 nodes as the most prominent feature. The branches of the lower part of the figure are in the 

 same condition as those of tig. 20. (X <).) 



Upper Helderberg group. Near Caledonia, N. T. 



