PLATE XV A. 



MiCHELINA (PlEUEODICTYUM) CONVEXA. 

 {See Plate 15, for references.) 



Fig. 1. A large and unusually cylindrical form of this species, as it occurs in the Corniferous lime- 

 stone of Ontario. The diaphragms are veiy convex and vesicular. 



Fig. 2. A small specimen, preserving its broad subconical form vi^ith deep striated calyces. 



Fig. 3. A young group with deep striated calyces and very convex diaphragms. 



Fig. 4. A lateral view of the preceding specimen. 



Fig. 5. The basilar portion of a young group in which none of the cells have attained the full size, 

 and with scarcely an evidence of diaphragms preserved. 



Fig. 6. The under side of the preceding specimen, showing the pustulose epitheca, the growth 

 having commenced on what appear to have been some broken cells of the species. 



Fig. 7. An enlargement of some solid colunms or filling of cells, preserving the striated surfaces 

 and minute pores. 



Fig. 8. A single cell enlarged to show the stria; and minute connecting pores, and the continuous 

 diaphragms. 



Fig. 9. An enlargement of .several columns or cell-fillings in limestone, showing the stria; and 

 irregular connecting pores. 



Fig. 10. An enlargement of some weathered open cells which preserve the striae and the margins 

 of some of the diaphragms, but .show no connecting pores. 



Fig. 11. The base of a young colony, showing the walls perforated with numerous pores, but with- 

 out evidence of diaphragms. 



