PLATE XIII. 



COSCINOTRYPA. 



(Page 537.) 



CoSCINOTRYPA CRIBRIFOEMIS, Hall. 



Figs. 1-4. Fragments, natural size. 

 Fig. 5. A portion of a frond. x6. 



Fig. 6. An enlargement from another specimen, showing the denticu- 

 lated cell apertures. x6. 

 Fig. 7. A transverse section, showing one of the elevations, a feature 

 characteristic of this genus, natural size. 

 Upper Helderberg group. Falls of the Ohio. 



COSCINIUM. 



(Page 537.) 



COSCINIUM STRIATUM, Hall. 



Fig. 8. A specimen, natural size. 



Fig. 9. An enlargement of a portion of fig. 8. 



Fig. 10. A still further enlargement, showing the denticulated cell 



apertures. xl8. 

 Fig. 11. A transverse section of the portion of the frond between the 



fenestrules. x6. 

 Fig. 12. One of the cell apertures. x72. 



Hamilton group. Widder, Ontario. 



f44: 



