PLATE XXXIX—Continued. 
Fenestella (Polypora) hexagonalis var. foraminulosa. 
Page 165. 
16. A portion of the non-celluliferous face of a frond, natural size. 
17. A portion of the celluliferous face of a frond, natural size. 
18. An enlargement of a portion of fig. 16, showing the character and comparative size of the 
branches and dissepiments; on the right of the figure the dissepiments form the bases of 
branches growing at right angles to the others. {X 6.) 
19. An enlargement of a portion of fig. 17, showing the form and comparative size of the branches 
and dissepiments, the form and arrangement of the cell apertures, and the prominent nodes 
characteristic of this variety. (X 6.) 
20. An enlargement of another portion of fig. 17, showing the non-celluliferous space, immediately 
below the bifurcations, continued downward between the central ranges of cell apertures in 
the form of a gradually narrowing shallow groove. The fenestrules are somewhat wider than 
those of fig. 19. (X 6.) 
Upper Helderberg group. Walpole, Ontario, Canada. 
