PLATE XXIII A. 



Callopora (Ccelocaulis) vknusta. 



Page 23. 

 See Plate 12. 

 Fig. 1. An enlargement showing the foi-m and arrangement of the cell apertures, and their strongly 

 elevated, and inflated margins. The nie.wpores are obsolete. (X IS.) 

 Lower Helderberg group. Clarkiville, N. T. 

 Fig. 2. An enlargement showing the form and arrangement of the cell apertui-es with thin slightly 

 elevated margins. (X 18.) 



Lower Helderberg group. ClarksviUe, N. Y. 

 Fig. 3. An enlargement showing the cell apertures disUmt from each other, irregularly disposed and with 

 u.sually a single row of mesopores between a^ljacent apei-tui-es. (X If.) 

 Ijower Helderberg group. Clarksmlle, N. Y. 

 Fig. 4. An enlargement showing irregularly disposed cell apertures and numerous prominent nodes on 



the elevated jieri8t<ime8. 



Lower Helderberg group. ClarksviUe, N. Y. 



Pig. 5. An enlargement showing irregularly disposed cell apertures and comparatively large mesopores. 



(X 18.) 



Lower Helderberg group. Clarkimlle, N. Y. 



CaI.LOI'OKA cellulosa. 



Page n. 

 See Plates 12 and 13. 

 Fig. 6. An enlargement showing irregularly disposed, distant cell apertui-es and numerous comparatively 

 small mesopores. (X 18.) 



Lower Helilerberg group. ClarksviUe, N. Y. 



Pig. 7. 



DiAMESOPORA rONSTRICTA. 

 Page 19. 

 See Plate 10. 

 An enlargement showing the foi-m of the cell ap»;rtui'es. (X 18.) 

 Lower Helderberg group. C laikscille, N. Y. 



FlSTULIPOKA PONDEROSA. ,„,„.. ^^ gf ^^^ 



Page i7. 

 See Plate 14. 

 Fig. 8. An oblique view of a si)orimen, showing the conical fonn of the nodes of the surface. (X 18.) 

 Lower Helfli'i>)erg group. Schoharie, iV. Y. 



Pig. 9. An enlargement showing the appearance of a specimen when the surface has been worn or 

 marcerated. (X 18.) 



Lower Helderl)erg group. Catskill creek, near CatukUl, 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 metiopores and the numerous prominent conical nodes. 

 (X 18.) 



Lower Helderberg group. C larks mile, N. Y. 



Callopora (Ccelocauli.s) mediopora. 



Page 'i.i. 

 See Plate 14. 

 Fig. 11. An eulargemeut showing elongate oval cell ai)erturu8 and mesopores which are fi-equently equal 

 in size to the cell apertures. (X 18.) 



Lower Helderljerg group. ClarksviUe, N. Y. 

 Fig. 12. An enlargement showing larger and moi-e broadly oval cell apertures than in the preceding figure, 

 with minute mesopoi-es and small spines on the elevated mai'gins of the apertures and meso- 

 poi-es. (X 18.) 



Lower Helderberg group. ClarksviUe, N. Y. 

 Fig. 13. An enlargement showing small cell apertures which ai-e sometimes nearly circular, and the meso- 

 pores which are sometimes larger than the apertures. (X 18.) 

 Lower Helderberg group. ClarksviUe, N. Y. 



