PLATE XXV. 



Callopora genicolata. 



Page 75. 

 Fig-. 1. A specimen, natural size, showing foi'm and mode of p-rowth. 



Upper Helderberg group. Ontario, Caimda. 

 Pig. 2. All enlargement of a portion of the pi-eceding, showing the form and arrangement of the cell 



ajiertures and intermediate pits. (X 6.) 

 Fig. 3. The interior of the same, showing the form and manner of growth of the cell tubes. 



Trematopoka (TkemAtella) 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 an-angeraent of the cell apertures and 

 ornamentation of the inter-apertural space. (X 18.) 



Caixopoka MULTKSEKIATA. 

 Page 75. 

 See Plate 26. 

 Fig. 6. A fragment, natural size. 



Upi)er Helderl)erg group. Near Leroy, Oenexee Co., N. Y. 

 Fig. 7. A portion of the i)rereding, enlarged, showing the form and arrangement of the cell apertures 

 and intermediate pits. (X 18.) 



, ,,,,i ACANTUOCLEMA ALTEKNATUM. 

 Page n. 

 Fig. 8. A fragment of a specimen, natural size, showing the fonn and mode of growth. 



Upiier Helderberg groiiji. (/iioiidaga Valhy, N. Y. 

 Fig. 9. A portion of the i)receding, enlargeil. showing the surfa<;e charactei-s, the form uiid ai-rangement 



of the cell ai)ertures, the alternating nodes and longitudinal ridges. (X 6.) 

 Fig. 10. A jmrtion of the same still further enlarged, showing moi-e distinctly the characters represented 

 in fig. 9. (X18.) , ,.,„^, , „, ^ ,„ ,;., 



LlCU£XALIA (LiOHENOTRYPA) IX)NGI8PINA. 



Page ac. 

 Fig. 11. A jKirtion of the surface, showing the form and arrangement of the cell apertures, the partitions 

 with Hpin<w at the angles. (X <>.) 



Upper Helderberg gnmp. Falls of the Ohw river. 

 Fig. 12. A portion of the same, showing the form of thi; ci-Il ii|M'rtui-e8 before the formation of the dividing 

 walls. (X 18.) 



LiCHENAUA (SeLENOPOUA) CIUCINCTA. 

 Page Mi. 

 Fig. 13. A s|>ecifflen, natural size, encrusting Potij}Kmi rultellata. i 



Upper Hehlerberg group. Falls of thi OhUi river. ■, , 



Fig. 14. Apdi-tionof the surface of the same, showing one of the uiaculje and a<lja4-ent cell ajiertunw. (XB.) 

 Fig. 15. A portion of the surface, showing more distinctly the form and arrangement of the cell apei-tui-es, 

 the lunate denticulations of the jteristomes and the elevations separating them. (X 18.) 



Trematopora (Trematella) arborea. 



PageW. 

 Pigs. 16, 17, 18, 20. Four specimens, natural size, showing variation in the mode of gi-owth and method of 

 branching. 



Upper Helderberg group. FWU of the Ohio river. 

 Fig. 19. An enlargement of a, portion of lig. 18, showing oval cell apertures, and areas destitute of aper- 

 tures, with the lower portion of the siii-face s|)inulo8e. (X 6.) 

 Fig. 21. A portion of tig. 2<l enlargeil. showing distinct annulations, the apertui-es obscured by abrasion 



and a portion of the surfu'c graniUose. 

 Fig. 24. The base of a frond, probably of T. arborea. 



