PLATE XXV. 
Callopora geniculata. 
Page 75. 
Fig. 1. A specimen, natural size, showing form and mode of growth. 
Upper Helderberg group. Ontario, Canada. 
Fig. 2. An enlargement of a portion of the preceding, showing the form and arrangement of the cell 
apertures and intermediate pits. (X 6.) 
Fig. 3. The interior of the same, showing the form and manner of growth of the cell tubes. 
Trematopora (Trematella) glomerata. 
Page 70. 
Fig. 4. A specimen, natural size, showing form and mode of growth. 
Upper Helderberg group. 
Fig. 5. A portion of a branch enlarged, showing the form and arrangement of the cell apertures and 
ornamentation of the inter-apertural space. (X 18.) 
Callopora multiseriata. 
Page 75. 
See Plate 26. 
Fig. 6. A fragment, natural size. 
Upper Helderberg group. Near Leroy, Genesee Co., N. Y. 
Fig. 7. A portion of the preceding, enlarged, showing the form and arrangement of the cell apertures 
and intermediate pits. (X 18.) 
Acanthoclema alternatum. 
Page 72. 
Fig. 8. A fragment of a specimen, natural size, showing the form and mode of growth. 
Upper Helderberg group. Onondaga Valley, N. Y. 
Fig. 9. A portion of the preceding, enlarged, showing the surface characters, the form and arrangement 
of the cell apertures, the alternating nodes and longitudinal ridges. (X 6.) 
Fig. 10. A portion of the same still further enlarged, showing more distinctly the characters represented 
in fig. 9. (X 18.) 
Lichenalia (Lichenotrtpa) longispina. 
Page 287. 
Fig. 11. A portion of the surface, showing the form and arrangement of the cell apertures, the partitions 
with spines at the angles. (X 6.) 
Upper Helderberg group. Falls of the Ohio rivet'. 
Fig. 12. A portion of the same, showing the form of the cell apertures before the formation of the dividing 
walls. (X 18.) 
Lichenalia (Selenopora) circincta. 
Page 86. 
Fig. 13. A specimen, natural size, encrusting Polypora cultellata. 
Upper Helderberg group. Falls of the Ohio river. 
Fig. 14. A portion of the surface of the same, showing one of the maculae and adjacent cell apertures. (X 6.) 
Fig. 15. A portion of the surface, showing more distinctly the form and arrangement of the cell apertures, 
the lunate denticulations of the peristomes and the elevations separating them. (X 18.) 
Trematopora (Trematella) arborea. 
Page 69. 
Figs. 16, 17, 18, 20. Four specimens, natural size, showing variation in the mode of growth and method of 
branching. 
Upper Helderberg group. Falls of the Ohio river. 
Fig. 19. An enlargement of a portion of fig. 18, showing oval cell apertures, and areas destitute of aper¬ 
tures, with the lower portion of the surface spinulose. (X 6.) 
Fig. 21. A portion of fig. 20 enlarged, showing distinct annulations, the apertures obscured by abrasion 
and a portion of the surface granulose. 
Fig. 24. The base of a frond, ; probably of T. arborea. 
