42 



XORTH AMERICAN INDEX FOSSILS. 



rounded knobs in which the rods terminate on the surface, these 

 being separated by a little more than half their diameter. Middle 

 Devonic limestones of Ohio and Michigan (Traverse group). 



FlG. 65. Stylodictyon columnare with enlarged vertical section (Nicholson, Pal. Ohio). 



IV. Stromatoporella Nicholson. 



Coralline mostly a lamillar expansion, furnished with a basal 

 epitheca. Latilaminae imperfect or not developed. In vertical 

 section concentric lamellae and radial pil- 

 lars distinguishable. In tangential sections 

 the ends of the pillars are distinguishable, 

 while the general character of the tissue is 

 reticulate ; short irregular zobidal tubes 

 present. Devonic. 

 9. S. granulata Nicholson. (Fig. 61, c, 



66.) Mid-Devonic. 



FlG. 66. Stromatoporella 

 granulata enlarged vertical 

 Fig. 67. Stromatoporella tuber culata (after Nichol- section, 

 son). 



Laminar expansions with concentrically wrinkled and striated 

 epitheca. Thickness from 2 mm. up to 2 or 3 cm. Rather dis- 



