12 



Prof. H. A. Nicholson on sovie new or 



tubercles, which may be about ^ millini. in heiglit, and 

 about the same diameter at their base. The tubercles may 

 be placed about ^ to j millim. apart, or may be in contact, 

 often coalescing in sinuous rows. The apices of the tubercles 

 may be simply rounded or pointed, and may be apparently 

 imperforate. In other cases a distinct circular aperture may 

 be detected at the apex of a pillar, though it is not clear that 

 this is not the result of weathering. 



Vertical sections (woodcut, fig. B) show that the coeno- 

 steum is essentially composed of very stout radial pillars. 





!A"«-Ci 



<: 1 





'"I^Oi- ? 





Sections of Lahechia conferta, Lonsd., sp., enlarged twelve times, ^^'en- 

 lock Limestone, Ironbridge : — A. Tangential section. B. Vertical 

 section, ^j ^) radial pillars ; c f, connecting processes or "arms." 



which spring from the basal epitheca and are continued to 

 the upper surface, where they terminate in the prominent 

 tubercles above spoken of. The interspaces between the 

 pillars are occupied by a vesicular tissue formed by the coales- 

 cence of connecting processes, or " arms," given out from the 

 pillars, the convexities of the vesicles being turned towards 

 the upper surface. 



