HYDROCORALLINES— STROM ATOPOROIDEA. 41 



Fig. 63. Clathrodidyon vesiculo 

 sum under or epithecal portion. 



centrically around elevated areas. Numerous minute rounded 

 tubercles, alternating with minute pores on well preserved surfaces. 

 No astrorhizae. Coarse (5 laminae to 1 mm.) radial pillars like 



spines growing downward from bot- 

 tom of laminae. 



This is, according to Nicholson 

 and Hinde, the common species of 

 the Niagara of Canada, usually re- 

 ferred to as Stromatopora concen- 

 tric a. 



6. C. ostiolatum Nicholson. Siluric. 

 Differs from the preceding in the 

 presence of nipple-like elevations of 

 the entire mass at intervals, and in 

 the occurrence of small perforated 

 tubercles at regular intervals in diagonal lines. 

 In the Gueiph of Canada and New York. 



7. C. cellulosum Nicholson & Murie. (Fig. 64.) Devonic. 

 Differs from C. vesicidosiun in the coarser mesh work (about 2 



laminae to I mm.) and in having the surface covered with tubercles 

 or granules; and from C. striatcllum in the 

 coarser mesh work. 



Onondaga limestone of Canada, New 

 York, etc. 



III. Stylodictyon Nicholson & Murie. 

 Ccenosteum a dense tissue traversed by 

 numerous closely set circular vertical col- 

 umns of large size, formed by the upward 

 bending of the concentric laminae. They 

 terminate on the surface in small pointed 

 eminences. Between the columns the tis- 

 sue is more open, consisting of horizontal 

 laminae and vertical (radial) pillars, the 

 latter often imperfect. Devonic. 



8. S. columnare Nicholson. {S.wortlieni 

 Quenstedt.) (Fig. 65.) Devonic. 

 A large mass readily recognized by the vertical rods of dense 



tissue formed by the upward bending of the laminae, and the small 



Fig. 64. 

 cellulosum. 

 son.) 



Clath rodictyon 

 (After Nichol- 



