PLATE XIX. 

 TREMATOPORA. 



(Page 591.) 

 Tbematopora tfberculosa, Hall. 

 Figs. 1, 2, 3. Fragments of this species, natural size. 

 Fig. 4. A portion of a branch showing the form and arrangement 

 of the cell apertures, and the monticules destitute of cell 

 apertures. xl8. 

 Fig. 5. An enlargement of a thin section showing the cell tubes and 

 the tabulated mesopores. xl8. 

 Niagara group. Lockport, N'. Y. 



TREMATELLA. 



(Page 550.) 

 Trematblla annulata, Hall. 

 Figs. 6, 7. Specimens, natural size. 

 Fig. 8. A portion of a branch. x6. 



Fig. 9. An enlargement of a thin section showing the internal 

 structure. 

 Upper Helderberg group. Falls of the Ohio. 



RHOMBOPORA. 



(Page 550.) 

 Rhombopora regularis, Hall. 

 Fig. 10. A group of specimens, natural size. 

 Fig. 11. A portion of a branch. xl8. 



Upper Helderberg group. Falls of the Ohio, 



Rhombopora transversa. Hall. 

 Fig. 12. A portion of a branch of this species. x6. 

 Fig. 13. An enlargement of a thin section showing the internal 

 structure. x6. 

 Hamilton group. Hamhatgh, N. Y. 



STREBLOTRYPA. 



(Page 551.) 

 SrREBLOTRTPA Hamilionense, Hall. 

 Fig. 14. An enlargement showing the regular arrangement of the 

 cell apertures, the interapertural pits, and the sinuous 

 ridges. x6. 

 Fig. 15. An enlargement from a specimen having unusually large 

 cell apertures, and without the prominent longitudinal 

 ridges. 

 Hamilton group. West Williams y Ontario, 



656 



