PLATE V. 



Fig. i. Transverse section of Pachypora (Favosites) cristata, E. and H., enlarged 



seven times, showing the thickening of the tubes by a secondary deposit 



of sclerenchyma. From the Wenlock Limestone of Dormington, near 



Stoke-Edith. 

 Fig. i a. Vertical section of the same, showing the thickened walls, tabulae, 



and mural pores, enlarged seven times. 

 Fig. i b. Vertical section of another specimen of the same, from Benthall 



Edge, showing the tabulae, together with numerous septal spines ; enlarged 



seven times. 



Fig. 2. Fragment of Striatopora Linneana, Billings, from the Hamilton forma- 

 tion of Ontario, of the natural size. 



Fig. 2 a. A small portion of the surface of the same, enlarged five times. 

 Fig. 2 b. Transverse section of a branch of the same, enlarged seven times. 

 Fig. 2 c. Portion of a tangential section of the same, enlarged seven times, 



showing the thickened walls, and spine-like septa. 

 Fig. 2 d. Part of a vertical section of the same, enlarged seven times, showing 



the thickened walls, the occasional tabulae, and the mural pores. 

 Fig. 3. Fragment of Trachypora ornata, Rom., from the Hamilton formation 



of Erie County, New York, of the natural size. 

 Fig. 3 a. Small portion of the surface of the same, enlarged five times, showing 



the ornamentation. 

 Fig. 3 b. Vertical section of the same, enlarged seven times, showing the 



thickened walls, the occasional tabulae, the numerous spiniform septa, and 



the few mural pores. 

 Fig. 3 c. Tangential section of the same, enlarged seven times, showing the 



thickening of the walls by concentric lamellae of sclerenchyma and the 



rudimentary septa. 

 Fig. 4. Fragment of Trachypora elegantula, Bill., from the Hamilton Group of 



Arkona, Ontario, of the natural size. 

 Fig. 4 a. Small portion of the surface of the same, enlarged five times, showing 



the peculiar ornamentation. 



Fig. 4 b. Transverse section of a branch of the same, enlarged five times. 

 Fig. 4 c. Vertical section of a branch of the same, enlarged seven times, show- 

 ing the immense thickening of the corallites by the deposition in their 



interior of successive laminae of sclerenchyma. 



