PLATE XXIX. 
SCALARIPORA SUBCON CAVA. 
Page 100. 
Fig-. 1. A fragment, natural size. 
Fig-. 2. A transverse section of a branch, showing- its form, the celluliferous seal®, the internal radiating 
mesotheca, and the intercellular vesicular structure, (X 6.) 
Fig. 3. An enlargement of one of the faces, showing the scahe and the form and arrangement of the cell 
apertures. (X 6.) 
Upper Helderberg group. Falls of the Ohio river. 
Scat.a ri pora scalariformis. 
Page 100. 
Fig. 4. A fragment, natural size. 
Fig. 5. An enlargement of one of the faces of a fragment, showing the scale and the form and arrange¬ 
ment of the cell apertures. (X 6.) 
Fig. 6. A view, looking directly upon one of the angles, showing, the angular margins, the scalae of two of 
the faces and the form and arrangement of the <-<>11 apertures. (X 6.) 
Fig. 7. An oblique view of one of the faces, showing the concavity of the surface, the arrangement of the 
external celluliferous scala;, and the form and disposition of the cell apertures. (X li.) 
Fig. 8. A transverse section of a branch, showing the form of the celluliferous seal®, the radiating- meso¬ 
theca and the divergent cell tubes. (X 6.) 
Upper Helderberg group. Falls of the Ohio river. 
Prismopora TRIQUETRA. 
Page 97. 
See Plate 28. 
Figs. 9, 10, 11. Fragments, natural size, showing- the ordinary variations in form and appearance. 
Fig. 12. A portion of one of the faces of a frond enlarged, showing the nbn-Celluliferous margins, and the 
form and arrangement of the cell apertures. (X 6.) 
Fig 13. An enlargement, of the surface from near the margin of one of the faces, showing the very 
oblique cell apertures, with prominent denticulate margins; the denticulations giving to the 
apertures a subtrilobate form. (X 18.) 
Fig. 14. An enlargement from another specimen, showing the ranges of apertures separated by prominent 
ridges; the denticulations of the cell margins are much more conspicuous than in figure 13. 
(X (3.) 
Fig. 15. A transverse section of a branch, showing the concave faces, the radiating- plates or mesothecse 
and the upright portion of the cells. 
Upper Helderberg group. Falls of the Ohio river. 
Prismopora paucirama. 
Page 98. 
See Plate 28. 
Fig. 16. A fragment, natural size. 
Fig. 17. An enlargement of one of the faces, showing the form and arrangement of the cell apertures. (X 6.) 
Upper Helderberg group. Onondaga Valley, Onondaga County, N. Y. 
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