PLATE XXXI—Continued. 
Fig. 24. 
Fig. 25. 
Fig. 26. 
Fig. 27. 
Fig. 28. 
Fig. 29. 
Fig. 30. 
Fig. 31. 
Fig. 32. 
Fig. 33. 
Fig. 34. 
Fig. 35'. 
Fig. 36. 
Fig. 37. 
Fig. 38. 
Fig. 39. 
Fig. 40. 
Fig. 41. 
An oblique view of the surface, showing the projecting posterior margins of the cell aper¬ 
tures. (X 6.) 
A vertical section of a thin lamina incrusting a Festestella, and showing prominent posterior 
cell margins. (X 6.) 
A portion of the surface of a specimen enlarged, showing the denticulate peristomes at right 
angles to the general surface, with the intermediate space bullate. (X 18.) 
An enlargement of the surface of a specimen where the cell apertures, on the lower part of the 
figure, are very oblique, while in the upper portion they are nearly rectangular to the surface, 
with a bullate intermediate .space. This latter feature is obscurely shown on some parts of 
the surface where the cells are oblique. 
Upper Helderberg group. Falls of the Ohio river. 
. 
LlCHENALIA LUNATA, iVill'. TUBULATA. 
Page 78. 
A fragment of a tubular specimen, natural’ size. 
An enlargement of a portion of the preceding, showing the form and arrangement of the den¬ 
ticulate apertures. (X 6.) 
Upper Helderberg group. Falls of the Ohio river. 
.98 i« ! p.'tfKuui .noniiooqH r. 1o fnemgrrfi A .01 .gUI 
LlCHENALIA (PiLEOTKYPa) CL1VULATA. 
Page 83. 
A fragment of a tubular ramose form, natural size. 
A portion of the surface enlarged, showing one of the monticules and adjacent cell apertures. 
A portion of the surface further enlarged, showing an irregular disposition of the cell apertures, 
marked by the prominent peristomes which are excessively developed on the posterior side, 
and the intermediate nodulose surface. (X 18.) 
A vertical section, showing the oq>en cells and the regularly septate intercellular space. (X 6.) 
Upper Helderberg group. Falls of the Ohio river. 
Phractopora cristata vav. lineata. 
Page 99. 
A fragment, natural size. 
An enlargement of the surface of the preceding, showing the character of the cell apertures and 
the narrow slightly elevated crests traversing the surface. (X 6.) 
Upper Helderberg group. Falls of the Ohio river. 
Phractopora cristata. 
Page 99. 
A portion of a frond, natural size. 
An enlargement from the surface of the preceding, showing the character of the cell aper¬ 
tures. (X 6.) 
A section through the carinse, showing the radiating mesotheca, the cells and intercellular struc¬ 
ture. (X o.) 
Upper Helderberg group. Falls of the Ohio river. 
LlCHENALIA ALTERNATA. 
Page 80. 
A fragment, natural size. 
A portion of the surface enlarged, to show the character and arrangement of cell apertures. (X 6.) 
A portion of the surface still further enlarged and presenting a somewhat different aspect of the 
cell apertures. 
Upper Helderberg group. Falls of the Ohio river. 
