PLATE XXVI. 



Tkematoi'oka (Tkematella) annulata. 



Pase 69. 

 See Plate 25. 

 Fig. 1. Showinff the natui-al size and manner of sfrowth. 



Fig. 2. The same, eiilai-g-ed. showing- the form and arrangement of cell aiiertures, and the anniilated 

 appeal ance of the branches. (X t>.) 



Upper Helderberg group. FiUls of the Ohio river. 



Trematopora (Orthopora) KHOMBIFERA. 



Page 71. 

 See Plates 11, 23 and 25. 

 Fig. 3. A specimen, natural size, showintr the manner of growth. 



Fig. 4. The same, enlarged, showing the form and aiTangeuient of .cell apertui-es, and granulose char- 

 acter of intercellular space. (X t>.) 



Upj>er Helderbcrg group. Falls of the Ohio river. 



Trematovora (Orthopora) regularis. 



Page 71. 

 See Plates 11, 13, %i and 25. 



Fig. 5. A s|)frimeu, natural size, showing the manner of growth. 



Fig. 6. The same, enlarge<l. showing the fonn and arrangement of the cell apertures, and the jiustu- 

 lose intercellular spaces. 



Upper Helderlicrg group. Fhllg of the Ohio rinr. 



Trematopora (Orthopora) .scutulata. 



Page 70. 

 Fig. 7. A s|)ei-inien, natiinil size, showing the manner of growth. 



Fig. 8. The same, enlarged, showing the fonn and arrangement of cell apertures, and the spinules at 

 the angles of the cell walls (X C) 

 Upper Heldertierg group. 



DlAMK.SOI'ORA CAMERATA. 



Page 72. 

 Fig. 9. A 8j)ecimen. natural size. 



Fig. 10. The same, enlarge<l, showing the form and arrangement of cell apertures, and the non-cellulifer- 

 ouM spaces. (X •"'-) 



Up|>er Helderberg gTt>U|i. Near Caledonia, N. T. 



OaLLOPORA (CoSLOCAUUS) IRREGCLARI8. 

 Page 78. 

 Fig. 11. Natural size of a spe<;imeu, showing the manner of growth. 



Fig. 12. An enlargement of fig. 11, showing the comparatively small cell ap»rture8, whichare distantly 

 and irregidarly arranged on one portion of the frond, and more closely arranged and with 

 intermediate i>itfl on the other. (X 6.) 

 Fig. 13. Another specimen, natural size, larger than that of fig. 11, and somewhat compr-eased. 

 Fig. 14. An enlargement of cme portion of fig. 13, showing cells somewhat more closely arranged than in 



fig. 12 ; with no inf<-rmediate jiits, and with macular destitute of cell aiiertures. (X 6.) 

 Fig. 15. An enlargement of another portion of fig. 13, .showing the cell apertures still larger, and arranged 

 in quite regular an'hing transverse rows. The peristomes composing the rows are fre- 

 quently in contact. (X 6.) 



Upper Helderberg' group. Central New York. 



