PLATE LIV. 
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Fenestella (Unitrypa) fastigata. 
Page 141. 
1. A fragment, natural size, showing the carina and connecting processes. 
2. The same fragment, natural size, showing the non-celluliferous side. 
3. A lateral view of a branch enlarged, showing a transverse section of the dissepiments and con¬ 
necting processes or scalse. (X 6.) 
4. A transverse section of the branches, also showing the depth of the connecting- seal®. (X 6.) 
5. An enlargement of a portion of the non-celluliferous face of a frond. (X 6.) 
6. An enlargement of the summits of the carinse and the connecting scalse. (X 6.) 
Upper Helderberg group. Falls of the Ohio river. 
Fenestella (Unitrypa?) consimilis. 
Page 142. 
7. An enlargement of the summits of the carinse and connecting scalse. This form might very 
readily be mistaken for the non-celluliferous face of other Fenestelloid forms. (X 6.) 
8. An enlargement of the celluliferous face of a frond ; the carina is broken away, showing the form 
and arrangement of the cell apertures. (X 6.) 
9. An enlargement; the two branches on the right have the surface broken away, showing the 
interior ; the next two branches have the carina broken away and show the form and arrange¬ 
ment of the cell apertures ; the left of the figure shows the summits of two carinse and their 
connecting scalse. (X 6.) 
Upper Helderberg group. Walpole, Ontario, Canada. 
Fenestella (Isotrypa) conjunctiva. 
Page 143. 
10. An enlargement of a portion of the non-celluliferous side of a frond, showing somewhat flattened 
branches, with a row of nodes along the middle, and a poriform opening on nearly all the 
dissepiments. (X 6.) 
11. An enlargement, showing rounded branches without nodes and with very conspicuous openings in 
the dissepiments. 
12. An enlargement, showing the angular and carinated branches and dissepiments, with a few open¬ 
ings in the latter, and these on the lower portion ; in this respect differing from every other 
specimen. (X 6.) 
13. An enlargement, showing a mold, in the rock, of the celluliferous face, and the summits of the 
carinse. (X 6.) 
14. An enlargement of the summit of the carina and connecting scalse. (X 6.) 
15. An enlargement of the celluliferous face, the carinse having been broken away, showing the form 
and arrangement of the cell apertures. (X 6.) 
16. A lateral view of the upper half of a branch. (X 6.) 
17. A fragment of a frond, natural size, showing the summits of the carinse and connecting scalse. 
18. A fragment of the non-celluliferous face of a frond, natural size, showing the size of the branches 
and mode of growth. 
19. An enlargement, showing angular, carinated branches, which are straighter than those repre¬ 
sented in fig. 12 ; the poriform openings are on the upper side of the dissepiments. (X 6.) 
20. An enlargement, showing- the under sides of the summits of the carinse and their connecting 
scalse. (X 6.) 
21. An enlargement of the specimen illustrated by fig. 11, to show more plainly the striations on the 
branches and the character of the openings on the dissepiments. (X 18.) 
Upper Helderberg group. Walpole, Ontario, Canada. 
