PLATE XXIII a— Continued. 
Callopora PERELEGANS. 
Page 22. 
See Plate 12. 
Fig-. 14. An enlargement of a portion of the surface of a specimen, showing the form of the cell apertures 
and mesopores. (X IS.) 
Lower Helderberg group. Clarksville, 2V". Y. 
Ptilodictya tenuis. 
Page 39. 
See Plates 13 and 17. 
Fig. 15. An enlargement showing- the appearance of the cell apertures near the margin of a specimen. 
(X IS.) 
Lower Helderberg- group. Smi,gerland/.s creek , near Clarksville , N. Y. 
Stictopora papili.osa. 
Page 57. 
See Plate 13. 
Fig. Id. An enlargement showing the form and arrangement of the papillose cell apertures. (X IS.) 
Lower Helderberg group. Clarksville, N. Y. 
Stictopora gkanatula. 
Page 38. 
See Plate 11. 
Fig. 17. An enlargement of a portion of the surface of a specimen, showing the form and arrangement of 
the cell apertures, with the thin, slightly elevated granulose peristomes. (X 18.) 
Lower Helderberg group. Catskill creek, N. Y. 
Rhinooiotya ? GRANULOSA. 
Page 40. 
See Plate 17. 
Fig. IS. An enlargement of a portion of a specimen showing the form and arrangement of the cell apertures 
and the numerous granules of the surface. (X IS.) 
Lower Helderberg group. Catskill week, N. Y. 
Fig. 19. An enlargement of a portion of a very slender specimen, showing the form and arrangement of 
the cell apertures and the conspicuous granules of the surface. (X IS.) 
Lower Helderberg group. Clarksville, N. Y. 
Ptilodictya lirata. 
Page 38. 
See Plate 17. 
Fig. 20. An enlargement of a portion of a specimen, showing the form and arrangement of the cell aper¬ 
tures and the minute triangular pits thin. (X 18.) 
• Lower Helderberg group. Schoharie, N. Y. 
Stictopora alternata. n. sp. 
Fig. 21. An enlargement showing the form and arrangement of the cell apertures, and the elevated inter- 
apertural area. (X IS.) 
Lower Helderberg- group. Clarksville, IV. Y. 
Stictopora obsoleta. 
Page 37. 
Fig. 22. An enlargement of a portion of a specimen, showing the form and arrangement of the cell aper¬ 
tures and the wide non-Celluliferous margin. (X 18.) 
Lower Helderberg group. Clarksville, N. Y. 
