PLATE I. 



[ Unless otherwise stated, all the specimens figured are in the collection of the Author.^ 



Fig. 1. — Glathrodictyon striatellum, d'Orb. ; vertical section, enlarged 24 times, 

 showing the granular aspect of the skeleton-fibre, with indications of a median 

 dark line in the horizontal laminse. Wenlock Limestone, Ironbridge. 



Fig. 2. — Glathrodictyon cellulosum, Nich. and Mur. ; vertical section, enlarged 

 24 times. The specimen is silicified, and the cavities of the skeleton have first 

 been lined with a layer of minute crystals, and subsequently filled with transparent 

 silica, often containing orbicular masses. The skeleton-fibre is traversed by 

 minute transverse lines of a lighter colour than the rest of the fibre, probably 

 representing minute canals. Corniferous Limestone, Ontario. 



Fig. 3. — Stromatopora typica, Rosen ; tangential section, enlarged 24 times, 

 showing the minutely porous character of the skeleton-fibre. Wenlock Limestone, 

 Ironbridge. 



Fig. 4. — Stromatoporella granulata, Nich.; tangential section, enlarged 48 times, 

 showing the minute pores and channels in the skeleton-fibre. Hamilton Forma- 

 tion, Arkona, Ontario. 



Fig. 5. — Vertical section of the same, similarly enlarged, showing the minute 

 tubular spaces and the clear median line in the skeleton-fibre. 



Fig. 6. — Stromatopora Carteri, n. sp. ; tangential section, enlarged 48 times, 

 showing the porous skeleton-fibre. Wenlock Limestone, Ironbridge. 



Fig. 7. — Vertical section of the same, similarly enlarged, t t, zooidal tubes. 



Fig. 8. — Actinostroma clathratum, Nich. ; tangential section, enlarged 12 times, 

 showing the cut ends of the radial pillars. The section passes for the most part 

 along the plane of a horizontal lamina. Devonian, Dartington, South Devon. 



Fig. 9. — Vertical section of the same, similarly enlarged, showing the " con- 

 tinuous " radial pillars. 



Fig. 10. — Part of tangential section of the same, enlarged 48 times, showing 

 the presence of an axial canal in some of the radial pillars. 



Fig. 11. — Actinostroma clathratum, Nich. ; tangential section, enlarged 12 times. 

 The section passes partly along the plane of one of the laminae, and partly through 

 one of the interlaminar spaces. Middle Devonian, Grerolstein. 



Fig. 12. — Vertical section of the same, similarly enlarged. 



Fig. 13. — Part of tangential section of the same, enlarged 48 times, passing 

 along an interlaminar space, and showing the axial canals in the radial pillars. 



Fig. 14. — Stromatoporella granulata, Nich. ; surface magnified, and showing 

 the openings of the zooidal tubes on large round tubercles, the radial pillars 

 terminating in blunt imperforate tubercles. Corniferous Limestone, Ontario. 



Fig. 15. — Stromatoporella granulata, Nich. ; tangential section, enlarged 12 

 times, showing the transversely-divided, irregular zooidal tubes (t). Hamilton 

 Formation, Arkona, Ontario. 



