PLATE XXVIII. 



'"" LiCHENALIA, sp. ? ..,!,„.. / 



Fig. 1. An enlargement of a portion of the weathei-ed face of a specimen, showing the form and arrange- 

 ment of the recumbent portion of the cell tubes as they lie upon the epitheca. (X 6.) 

 Upper Helflerbei-g group. 



ACANTHOCLEMA DIVERGENS. 

 Page 73. 

 Fig. 2. The natural size of a specimen, showing the form and mode of branching. 

 Upper Helderberg group. Onondaga Valley, iV. Y. 



AcANTHOCLEMA OVATUM. 't" ^ ■" 



Fig. 3. An enlargement of a portion of a specimen, showing the form and arrangement of cell aper- 

 tures, with ridge.s separating the longitudinal ranges of apertures. (X 6.) 

 Upper Helderberg group. Onondaga Valley, JV. Y. 



StICTOPORA LINEARIS. 



Pa^ 9«. 

 See Plate 27. 

 Vig. 4. An enlargement of a portion of a specimen, showing the form and arrangement of cell aper- 

 .;: .,, tures, and the longitudinal ridges separating the range.s of upertui-es. (X 6.) , 



r\g. 6. An enlargement of a portion of a weathered specimen. The surface between the cell walls is 

 worn away, giving to the surface the appearance of having contiguous, quadrangular cell 

 apertures. 



Upper Helderberg group. New York. 



AcANTHOCLEMA TRISERIALE. 



Page 74. 

 Fig. 6. A specimen, natural size. 



V^ff^,.;.%i A portion of the preceding enlarged, showing the form and an'angement of the cell apertures, 



and the strong granulose ridges separating the longitudinal ranges. (X 6.) 



Upper Heldei-berg group. Near Caledonia, N. T. 



Prismopora triquetra. 



Page 97. 



See Plate 29. 

 Fig. 8. A specimen, natural size. 

 Fig. 9. An enlargement of a portion of a specimen, giving an oblique view of two of the three faces. 



(X6.) 

 Fig. 10. An enlargement from the same specimen, showing the concave face, and the form' and arrange- 

 ment of the cell ajiertures. : -iil'iH -liil'l 

 Upper Helderberg group. FhlU of the Ohio river. 



 Hinn --' 



Prismopora pauoiraha. 



Page 98. 

 See Plate 29. 

 ]?M(: ' l- ^" enlargement of a transverse section, .-ihowiiig the internal plates radiating from the center to 

 eaoh of the nnglen, a few of the cell tubes, and the intercellular vesiculose structure. (X 6.) 

 Upper Helderberg group. T)uniipson's lake, Albany Co.^ If. Y. 



