PLATE XXVII. 



Stiotopora linearis. 



Page 96. 

 See Plate 28. 

 Fig. 1. A fragment enlarged to six diameters. 



Upijer Helderberg group. Onondaga VaUey, Onondaga Co., N. Y. 



Stiotopora vermicula. 



Page 83. 

 Pig. 2. A specimen, natural size, showing the form and manner of bifurcation. 

 Pig. 3. The meaotheca enlargeil. showing the aivhing lines of growth, and tho diverging and undulating, 



longitndinal narrow lines formed by the recumbent portions of the cell tubes. (X 6.) 

 Pig. 4. The sui'face enlargeii, showing the arrangement and appearance of the cell apertures, some of 

 which are separated by longitudinal striie. fX "•) 



Upper Helderberg group. Ontario, Canada. 



Stiotopora crescens. 



Page 81. 



Pig. 5. A fragment, natural size. 



Pig. 6. A sjieciraen enlarged. The lower i)Ortion of the tigui-e shows the surface ; the upper portion, the 

 mesotheca with longitndinal striations and arching undulations of growth ; the central portion 

 of the figure presents the inner face of the opposite half, showing tho broken ends of the cell 

 tubes just below the ajwrtui-es and the vesicnlose slmctui-e between them. (X 6.) 



Fig. 7. The mesotheca enlarged, showing the longitudinal striations anil trltnsverae undulations. (X 6.) 



Rg. 8. A portion of the surface enlarged, showing the comparative size, form and arrangement of the 

 cell apertures, the longitudinal elevations, and the ol)li<iiie stiiie on the non-celluliferous margin 

 •of the frond. (X 6.) 



Pig. 9. A transverse section, showing the vertical portion of the cells. (X 6.) 



Fig. 10. A transverse section of a thinner branch. (X''-) 



Pig. 11. A long^tuilinal section, showing the form of the cell tubes and their manner of growth. (X 6.) 

 Upper Helderberg group. Ontario, Canada. 



>-■»•; 



WM&i 



Stiotopora ovatipora. 



PageM. 



See Plate 28. 

 Fig. 12. A sjiecimen, natui-al size. 

 Pig. 18. A transverse section, showing the interior chai-acter of the i-idges separating the longitudinal 



ranges of apertures. (X 6.) 

 Fig. 14. A transverse section, showing the vesicnlose intei-cellidar structure. (X 6-) 

 Pig. 15. All enlargement of a portion of the siii-fiure of a speriraen, showing the pu-stidiform api)earance 



of the cell aperture- ^' ■! *h" tiilol>nt<' form of tho o]ii>iiiiii^ jirodiweil by the lunate denticu- 



lations. (X 18.) 

 Pig. 16. A lateral view of a s|iociirii'ii, showing the elevation of the oi'llnles. (X •!•) 

 Fig. 17. A transverse section of the same specimen, showing the sharply carinate margins. (X 6.) 

 Fig. 18. An enlargement of a jKirtion of the surface of a specimen, showing the form and arrangement of 



the cell apertures. The denticulations are obsolete. (X 6.) 

 Pig. 19. An enlargement of the surface of another sjiecimen, showing the cell apertures more distinctly 



denticulated. 



Upper Helderberg gi-oup. fiUU of the Ohio river. 



