PLATE XI— Continued. 



TrEMATOPORA (OKTHOrOKA) KHOMBIFERA, Hall. 



Page 18. 



8«e Plate 23. 



Fig. 15. (16a.) Two specimens of natural size, showing the extremes of raze. 



Lower Helderberg group. Clarksvtlle, N. T. 

 Fig. 17. A specimen, natural size, having the principal branches nearly parallel with the main one, which 

 is bifurcated above. 



Lower Helderberg group. ClarktvUle, N. Y. 

 Pig. 18. A larger branching specimen, natural size. 



Lower Helderberg group. ClarksvUie, N. T. 

 Fig. 19. An enlargement showing the arrangement and form of apertures, with the interapertural partitions. 



Lower Helderberg group. Clarksvilte, N. T. 

 Fig. 20. An enlargement of a bifurcating branch where the cell apertures are constricted by the thickening 

 of the intei-cellular substance. 



Lower Helderberg grouj). Clarisville, N. T. 



StICTOPORA GltANATULA. 



Page 38. 

 See Plate 23 a. 

 Fig. 16. A specimen, natural size. 



Lower Helderberg group. CaUkill Greek, N. T. 



LiCHKNALIA 0RA8SA. 

 Page 30. 

 Fig. 21. A flattened or crushed branching form, showing a distinct poriferous surface. 

 Fig. 22. An enlargement from fig. 21, showing the round and regularly ai-ranged cell apertures in some 

 parts, while the macula are without cell apertui-es. 

 Lower Helderberg group. Schoharie, N. Y. 



Callopora (Callotrypa) macropora. 



Page 24. 

 See Plate 23. 

 Fig. 23. A weathered branching specimen, natural size. 



Lower Helderberg gi-oup. Catskill Creek, N. T. 

 Fig. 24. An enlargement from fig. 23. 

 Fig. 25. A bifurcating branch, natural size. 



Lower Helderberg grouji. ClarkuvUle, N. Y. 

 Fig. 26. An enlargement from the preceding, showing oval cell apertures and mostly one range of inter- 

 apertural pits. 

 Fig. 27. A slender, branching form of this species. 



Tentaculite limestone. Schoharie, N. Y. 



Fig. 28. A small branching fragment. 



Lower Helderberg group. Schoharie, N. Y. 

 Fig. 29. An enlargement from fig. 28, with larger cells than in fig. 26, and with few and irregularly dis- 

 posed interapertural pits. 



Callopora (Callotrypa) macropora var. signata. 



Pago 2S. 

 Fig. 80. A branching specimen, natural size. 



Fig. 31. An enlargement from the preceding, showing cell apertures with occasional interax)ertural pits. 



Lower Helderberg group. Clarksvtlle, N. Y. 



