PLATE XXV—Continued. 
Trematopora (Trematella) annulata. 
Page 69. 
See Plate 26. 
Fig. 22. A specimen, natural size. 
Upper Helderberg group. Falls of the Ohio river. 
Fig. 23. A portion of the surface of the preceding, showing the polygonal and closely arranged cell 
apertures. (X IS.) 
TrOPIDOPORA NANA. 
Page 71. 
Fig. 25. A specimen, natural size, associated with Anlopora and Fenestella. 
Fig. 26. A portion (X 18) showing the form and arrangement of the cell apertures and the undulating 
longitudinal ridges. 
Upper Helderberg group. 
Trematopora (Orthopora) regularis. 
Page 91. 
See Plates 11, 13, 23 and 26. 
Fig. 27. A fragment, natural size. 
Fig. 28. A portion (X 6) showing rows of granules between the cell apertures. 
Upper Helderberg group. Falls of the Ohio river. 
Trematopora (Orthopora) rhombifera. 
Page 71. 
See Plates 11, 23 and 26. 
Fig. 29. A specimen, natural size, showing an unusual mode of branching. 
Upper Helderberg group. Falls of the Ohio riven-. 
Nemataxts FIBROSUS. 
Page 74. 
Fig. 30. A specimen, natural size, imbedded in the rock, and fractured so as. to show the internal structure 
and also the mode of branching. 
Upper Helderberg group. 
Fig. 31. A portion of another specimen. The cell apertures are obsolete and the surface is marked by 
broad, somewhat irregular, longitudinal striations. (X 6.) 
Upper Helderberg group. 
Fig. 32. A portion of the surface of another specimen, presenting characters similar to those in tig- 31, 
but having finer and more regular striations. (X 6.) 
Upper Helderberg group. 
Fig. 33. A portion of a specimen broken below and showing the angular cell tubes. (X 6.) 
Upper Helderberg group. 
Fig. 34. A portion of a specimen, showing the oval cell apertures arranged in regular longitudinal rows 
and maculae destitute of cell apertures. (X 6.) 
Upper Helderberg group. 
Fig. 35. A portion of fig. 30, showing the cell tubes and the fibrous structure near the surface. 
Fig. 36. A portion of the interior of a specimen, showing- the direction of the cell tubes. (X 6.) 
