PLATE 11. 



Fenestella (Polypoka) arta. 



Figs. 1-3. 



Fenestella {Polypora) Ar-ta, Hall. Pal. N. Y., Vol. VI, page 63. 



Fig. 1. An enlargement from the non-celluliferous face of a frond with 



rigid, rounded branches, and nearly uniform fenestrules. 

 Fig. 2. An enlargement from the non-celluliferous face of a frond, where 



the branches are somewhat flattened and bifurcating above. 

 Fig. 3. An enlargement of two adjacent branches ; the one with three 



ranges of cell apertures, and the other with two ranges of cell 



apertures and a central carina. 18 x. 

 This figure is given to compare wuth Fenestella obliqua, fig. 4. 



Fenestella obliqua. 



Fig. 4. 



Fenestella {Polypora) obliqiia, Hall. Pal, N. Y., Vol. VI, page 64. 



Fig. 4. An enlargement of the celluliferous face of two branches with 



connecting dissepiments; showing the oblique arrangement of 



the outer ranges of cell apertures. 18 x. 



Fenestella peeplexa. 



Fig. 5. 



Fenestella perplexa, Hall. Pal. N. Y., Vol. VI, page 130 (not figured). 



Fig. 5. An enlargement of three branches from the celluliferous face, 

 showing the strong carina with prominent transverse bars. 

 Upper Helderberg group. 



Fenestella (Unitrypa) pkojecta. 



Figs. 6-8. 



Fenestella {Unitrypa) projecta, Hall. Pal. N. Y., Vol. VI, page 132 (not 



figured). 



Fig. 6, A portion of the non-celluliferous face of a frond, showing the 

 projections on the upper margins of the dissepiments. 



Fig. 7. An enlargement of three branches and the connecting dissepi- 

 ments, showing the characteristic features of the non-cellu- 

 liferous face. 



Fig. 8. A lateral view of a branch enlarged, showing sections of the 

 dissepiments, the cell aperture with projecting cell margins, and 

 the curving scales above. 



