PLATE XXVII. 
Stictopora linearis. 
Page 96. 
See Plate 28. 
Fig. 1. A fragment enlarged to six diameters. 
Upper Helderberg group. Onondaga Valley, Onondaga Co., IV. Y. 
Stictopora yermicula. 
Page 93. 
Fig. 2. A specimen, natural size, showing the form and manner of bifurcation. 
Fig. 3. The mesotheca enlarged,' showing the arching- lines of growth, and the diverging and undulating, 
longitudinal narrow lines formed by the recumbent portions of the cell tubes. (X 6.) 
Fig. 4. The surface enlarged, showing the arrangement and appearance of the cell apertures, some of 
which are separated by longitudinal strife. IX 6-) 
Upper Helderberg group. Ontario, Canada. 
Stictopora orescens. 
Page 91. 
Fig. 5. A fragment, natural size. 
Fig. 6. A specimen enlarged. The lower portion of the figure shows the surface ; the upper portion, the 
mesotheca with longitudinal striations and arching undulations of growth ; the central portion 
of the figure presents the inner face of the opposite half, showing the broken ends of the cell 
tubes just below the apertures and the vesiculose structure between them. (X 6.) 
Fig. 7. The mesotheca enlarged, showing the longitudinal striations and transverse undulations. (X 6.) 
Fig. 8. A portion of the surface enlarged, showing the comparative size, form and arrangement of the 
cell apertures, the longitudinal elevations, and the oblique strife on the non-celluliferous margin 
of the frond. (X 6.) 
Fig. 9. A transverse section, showing the vertical portion of the cells. (X 6.) 
Fig. 10. A transverse section of a thinner branch. (X ( >.) 
Fig. 11. A longitudinal section, showing the form of the cell tubes and their manner of growth. (X 6.) 
Upper Helderberg group. Ontario, Canada. 
StICTOPOR a O V AT IPO R A. 
Page 93. 
See Plate 28. 
Fig. 12. A specimen, natural size. 
Fig. 13. A transverse section, showing the interior character of the ridges separating the longitudinal 
ranges of apertures. (X 0.) 
Fig. 14. A transverse section, showing the vesiculose intercellular structure. (X 6-) 
Fig. 15. An enlargement of a portion of the surface of a specimen, showing the pustulifonn appearance 
of the cell apertures and the trilobate form of the openings produced by the lunate denticu- 
lations. (X 18.) 
Fig. 16. A lateral view of a specimen, showing the elevation of the cellules. (X 6.) 
Fig. 17. A transverse section of the same specimen, showing the sharply carinate margins. (X 6.) 
Fig. 18. An enlargement of a portion of the surface of a specimen, showing the form and arrangement of 
the cell apertures. The denticulations are obsolete. (X 6.) 
Fig. 19. An enlargement of the surface of another specimen, showing the cell apertures more distinctly 
denticulated. 
Upper Helderberg group. Falls of the Ohio river. 
