PLATE XXIII a. 
Callopora (Ccelocaulis) venusta. 
Page 23. 
See Plate 12. 
Fig-. 1. An enlargement showing the form and arrangement of the cell apertures, and their strongly- 
elevated, and inflated margins. The mesopores are obsolete. (X IS.) 
Lower Helderberg group. Clarksville, N. Y. 
Fig. 2. An enlargement showing the form and arrangement of the cell apertures with thin slightly 
elevated margins. (X 18.) 
Lower Helderberg group. Clarksville, N. Y. 
Fig. 3. An enlargement showing- the cell apertures distant from each other, irregularly disposed and with 
usually a single row of mesopores between adjacent apertures. (X IS.) 
Lower Helderberg group. Clarksville, i\ r . Y. 
Fig. 4. An enlargement showing irregularly disposed cell apertures and numerous prominent nodes on 
the elevated peristomes. 
Lower Helderberg group. Clarksville, N. Y. 
Fig-. 5. An enlargement showing irregularly disposed cell apertures and comparatively large mesopores. 
(X 18.) 
Lower Helderberg group. Clarksville, N. Y. 
CaLLOIORA CELLUL03A. 
Page 21. ' 
See Plates 12 and 13. 
Fig. 6. An enlargement showing irregularly disposed, distant cell apertures and numerous comparatively 
small mesopores. (X 18.) 
Lower Helderberg group. Clarksville, N. Y. 
DlAMESOPORA CONST PICT A. 
' Page 19. 
See Plate 10. 
Fig. 7. An enlargement showing the form of the cell apertures. (X 18.) 
Lower Helderberg group. Clarksville, N. Y. 
Fist u li po ra pond e rosa . 
Page 27. 
See Plate 14. 
Fig. 8. An oblique view of a specimen, showing the conical form of the nodes of the surface. (X 18.) 
Lower Helderberg group. Schoharie, N. Y. 
Fig. 9. An enlargement showing the appearance of a specimen when the surface has been worn or 
marcerated. (X IS.) 
Lower Helderberg group. Catskill creek, near Catskill, iV. Y. 
Fig. 10. An enlargement of a portion of the surface of a well preserved specimen, showing the form and 
arrangement of the cell apertures, the mesopores and the numerous prominent conical nodes. 
(X 18.) 
Lower Helderberg group. Clarksville, N. Y. 
Callopora (Cgelocaulis) mediopora. 
Page 23. 
See Plate 14. 
Fig. 11. An enlargement showing- elongate oval cell apertures and mesopores which are frequently equal 
in size to the cell apertures. (X 18.) 
Lower Helderberg group. C larksville, N. Y. 
Fig. 12. An enlargement showing larger and more broadly oval cell apertures than in the preceding figure, 
with minute mesopores and small spines on the elevated Margins of the apertures and meso- 
- pores. (X 18.) 
Lower Helderberg group. Clarksville, N. Y. 
Fig. 13. An enlargement showing small cell apertures which are sometimes nearly circular, and the meso¬ 
pores which are sometimes larger than the apertures. (X 18.) 
Lower Helderberg group. C larksville, N. Y. 
