PLATE L. 
Fig. 1. 
Pi g- 2. 
Fig. 3. 
Fig. 4. 
Fig. 5. 
Fig. 6. 
Fig. 7. 
Fig. 8. 
Fig. 9. 
Fig. 10. 
Fig. 11. 
8ucm‘irlifl 
Fenestella cultrata. 
Page 120. 
A fragment, natural size, showing the manner of growth. 
A transverse section of the branches. (X 0.) 
A lateral view of a branch, showing a transverse section of the dissepiments, and the irregular 
arrangement of the cell apertures. 
A portion of the non-celluliferous face of a frond. (X 6.) 
A portion of the celluliferous face. (X 6.) 
Upper Helderberg group. Falls of the Ohio river. 
Fenestella biserrulata. 
Page 128. 
A fragment natural size, showing the manner of growth. 
A transverse section, showing the form of the branches and carinse and the space occupied by 
the cells. (X 6.) 
A lateral view of a branch, showing a transvere section of the dissepiments, the cell apertures, 
the crenulations in the margin of the carina, immediately above and corresponding in number 
to the cell apertures. The projections on the side of the carina have somewhat the appear¬ 
ance of a range of minute cells, but the lithographic figure does not properly represent the 
original drawing. (X 6.) 
A portion of the non-celluliferous face of a frond, showing the comparative size and character of 
the branches and dissepiments. (X fi.) 
A portion of the celluliferous face, showing the cell apertures and also the expanded summits of 
the carinse with their lateral crenulations. The lithographic figure has failed to preserve the 
effect of the original drawing ; the same criticism will apply to fig. 11. 
An enlargement of a portion of the celluliferous face, having the carinse broken away, leaving 
the branch grooved along its center, showing the form and arrangement of the cell apertures, 
and their elevated margins slightly indenting the borders of the fenestrules, (X 6.) 
Upper Helderberg group. Falls of the Ohio river. 
Fenestella granifera. 
Page 125. 
Fig. 12. An enlargement of a portion of the non-celluliferous face, showing angular sinuous branches with 
dissepiments much wider than the branches. (X fi.) 
Fig. 13. An "enlargement of a portion of the non-celluliferous face, showing flattened branches and dissepi¬ 
ments, with a row of minute granules along the middle of the branch. The flattened branches 
and dissepiments would indicate that the specimen has been worn or macerated, but in that 
case it seems hardly possible that the granules should be so well preserved. 
Fig. 14. An enlargement of the celluliferous face of a portion of the frond from near the base, covered by 
an organic deposit, which forms a solid crust over that portion of the specimen. 
Fig. 16. A portion of the non-celluliferous face enlarged to six diameters ; the left side of the figure shows 
two branches in the same conditions as those of fig. 13 ; the two adjacent branches are appar¬ 
ently worn so that the cells are partially exposed ; the right of the figure shows the branches 
broken away so that the under sides of the expanded crenulate carinse are exposed. 
Upper Helderberg group. Near Le Roy, N. Y. 
