PLATE XXIII—Continued. 
Trematopora (Orthopora) NODOSA, 11 . sp. 
Fig. 10. An enlargement showing the form and arrangement of the cell apertures, their slightly elevated 
margins and the prominent nodes. (X 18.) 
Lower Helderberg group. Clarksville, N. Y. 
Trematopora (Orthopora) riiombifera. 
Page 18. 
See Plate 11. 
Fig. 11. An enlargement of a specimen, the surface of which has been somewhat weathered. 
Lower Helderberg group. Clarksville, N. Y. 
Fig. 12. An enlargement showing prominent nodes at the angles of the vestibular areas. 
Lower Heidelberg group. Clarksville, N. Y. 
Callopora (Callotrypa) striata. 
Page 26. 
See Plate 11. 
Fig. 13. An enlargement showing the form and arrangement of the cell apertures, the prominent node at 
the base of each aperture, and the mesopores so arranged that their margins have the appear¬ 
ance of longitudinal striations. (X 18.) 
Lower Helderberg group. Schoharie, N. Y. 
Fig. 14. An enlargement showing the cell apertures with slightly elevated margins, without nodes. The 
mesopores appear simply as interrupted striations. (X 18.) 
Lower Helderberg group. Schoharie, N. Y. 
Callopora (Callotrypa) macropora. 
Page 24. 
See Plate 11. 
Fig. 15. An enlargement showing the oval cell apertures with their equally elevated margins, which are 
frequently in contact. (X 18.) 
Lower Helderberg group. Clarksville, N. Y. 
Fig. 16. An enlargement showing cell apertures without elevated margins. The surface between the 
apertures is elevated, angular and with few mesopores. 
Lower Helderberg group. Clarksville, N. Y. 
Fig. 17. An enlargement showing the margins of the cell apertures distinctly and equally elevated and 
with two or three ranges of mesopores between adjacent cell apertures. (X 18.) 
Lower Helderberg group. Slingerland’s Creek near Clarksville, N. Y. 
Fig 18. An enlargement showing the cell apertures without elevated margings. Interapertural space 
elevated, rounded and with moderately prominent nodes. Mesopores few and often obsolete 
over a portion of the specimen. 
Lower Helderberg group. Clarksville, N. Y. 
Fig. 19. An enlargement showing the cell apertures polygonal in form, from mutal pressure and with con¬ 
spicuous mesopores. The peristomes are thin and strongly and equally elevated. (X 18.) 
Lower Helderberg group. Clarksville, N. Y. 
Trematopora? (Trematella?) corticosa. 
Page 15. 
See Plates 10 and 13. 
Fig. 20. An enlargement showing regularly oval cell apertures. (X 18.) 
Lower Helderberg group. Clarksville, N. Y. 
Callopora (Callotrypa) paucipora, n. sp. 
Fig. 21. An enlargement showing the form and arrangement of the cell apertures, the scattered mesopores 
and nodes. 
Lower Helderberg group. Clarksville, N. Y. 
