16 On 7iew or imperfectly-knoion Species of Stromatoporoids. 



which it could be confounded when its minute structure is 

 examined. 



Formition and Locality. Common in the C^rniferous Lime- 

 stone (Devonian) of Port Colborne, Ontario. 



EXPLANATION OF THE PLATES. 



[As the figures of minute structure are based upon photograph?, the 

 scale of magnification is not absokitely constant, but varies between ten 

 and twelve times. As a rule, the enlargement may be taken as being 

 abjut ten times the natural size. Where a different migaifying-pawer 

 has been used, or where the figures are of the natural size, this is speci- 

 ally stated.] 



Plate I. 



Fig. 1. Vertical section of thetype-speci'iien of Clathrodictjfon vcsicidosum, 

 Nich. & jNIur. Clinton formation, Yellowsprings, Ohio. 



Fiff. 2. Tangential section of the same. 



Fi(/. S. Vertical section of an example of C. vedculosum, from the Wen- 

 lock Limestone of Much Wenlock. 



Fig. 4. Surface of a broken fragment of Clathrodictyon variolare, Rosen, 

 sp., of the natural size. Silurian, Esthouia. 



Fiy. 5. Vertical section of C. variolare, Rosen, from the Silurian rocks of 

 Kattentack, Esthonia. 



Fiff. 6. Tangential section of the preceding specimen. 



Fig. 7. Vertical section of Clathrodictyon Limiarssoni, Nich., from the 

 Wenlock Limestone of Wisby, Gotland. A vertical astrorhizal 

 canal is cut through by tlie section. 



Fig. 8. Tangential section of the preceding specimen. 



Fig. 9. S'ertical section of Clathrodictyon striatcUum, d'Orb., from the 

 Wenlock Limestone of Dudley. 



Fig. 10. Tangential section of the preceding. 



Plate II. 



Fig. 1. Vertical section of Clathrodictyon crassuin, Nich., from the Wen- 

 lock Limestone of Ironbridge. 



Fig. 2. Tangential section of the same. 



Fiy. 3. Vertical section of Clatkrodictyoyi fastiyiatum, Nich., from the 

 Wenlock Limestone of Ironbridge. 



Fig. 4. Tangential section of the same. 



Fig. 5. Vertical section of Clathrodictyon regiihtre, Rosen, sp., from the 

 Wenlock Limestone of Dudley. 



Fig. 6. Tangential section of the same. 



Fig. 7. Vertical section of Clathrodictyon cellulomm, Nich. & Mur., from 

 the Corniferous Limestone of Ontario. 



Fig. 8. Tangential section of the same. 



Plate III 



Fig. 1. Clathrodictyon ostiolatum, Nich., vertical section, from the Silu- 

 rian (Guelph formation) of Guelph, Ontario. 



Fig. 2. Tangential section of the same. 



Fiy. 3. Surface of a fragment of the same, of the natural size, showing 

 the prominent apertures of the axial astrorhizal canals. 



