242 PROr. H. A. NICHOLSON AND DR. J. MURIE ON THE 



tiiberculate and granular surface, and also below, in side view, the 

 (weathered) series of undulating layers composing the thickness of the 

 specimen. About the natural size. 



Fig. 2. Another, smaller, piece of Stroonato'pora tuherculata, exhibiting the sur- 

 face of the concentric lamina, its granular intermediate structure and 

 protruding pillars with pseudo-orifices, X 3 diam. (from the Devo- 

 nian measures, Canada), and in which the skeleton has been silicified 

 and the filling up of the chambers calcareous. 



Fig. 3. A vertically exposed fragment of S. tuherculata, preserved in the same 

 way and decalcified by weathering. The chambers, horizontal lamina; 

 or concentric layers, and the vertical or radial pillars stand out in 

 relief. X 3 diam. 



Fig. 4. The form usually known as Stromatopora striatella, D'Orb. A transpa- 

 rent vertical section of an example from the Wenlock, Upper Silurian, 

 Gotland, Sweden. Seen under a 2-inch object-lens (=x20 diam.), 

 and, as in fig. 3, exhibiting the chambers, horizontal laminte, and radial 

 pillars. 



Fig. 5. A partly tangential and transverse section of the same piece of S. stria- 

 tella, x20 diam., and in which the cut ends of the radial pillars are 

 very manifest. 



Fig. 6. Another, chiefly vertical, section, but from the same specimen of S. stri- 

 tella, under a 1 -inch objective, X60 diam. The granular character of 

 the horizontal laminae and vertical pillars, and the occasional inter- 

 communication of the chambers by imperfection of the septa, are 

 markedly visible. 



Fig. 7. An oblique or tangential section of the so-called 8. striatella, also viewed 

 with an inch objective ( = x50 diam.). 



Fig. 8. Strojiiatopora nodulata, Nich. A transparent vertical section of a piece 

 from the Corniferous Limestone, Ohio. Twice nat. size. 



Fig. 9. A portion of the above specimen of S. nodulata, under a 2-inch object- 

 lens ( = X 20 diam.). In this figure the irregularity in size and shape 

 of the sarcodc-chambers and variability in thickness of the concentric 

 laminic and vertical pillars are noteworthy. The specimen itself shows, 

 what is barely represented in the drawing on stone, that both la- 

 minae and pillars, but especially the former, are remarkably granular 

 in consistence, and in many instances a series of subsidiary thin layers 

 compose each lamina, or give it a somewhat reticulate porous appear- 

 ance. 



Fig. 10. Stromatojpora mammillata, Nich. A small portion of the surface of an 

 extensive thin crust, exhibiting its conical elevations, a few of which 

 appear perforated. On the undulating granular intervening spaces, 

 rather indistinct however, are traces of stellse or radiate water-canals. 

 From the Corniferous Limestone of Port Colborne. Nat. size. 



Fig. 11. Stromatopora {Coenostroma'2) granulata, Nich. Stellar grooves or radiate 

 water-canals with surrounding miliary granulation on the weathered 

 surface of a portion of an undulating crust. Nat. size. 



Fig. 12. S.{C(Xnostro7na'i) granulata. A vertical transparent section, X 6 diam. 



This irregular-looking crust had grown and pushed its way among some 

 coral debris. Magnified more highly, portions of this specimen still 



