10 Prof. H. A. Nicholson on some new or 



Stromatoporella granulata, Nich. 



Stromatopora granulata, Nicliolsou, Aiiu. & Mag. Nat. Hist. ser. 4, 

 vol. xii. p. 94, pi. iv. figs. 3, 3 a (1873). 



Coenosteum forming laminar expansions, attached basally 

 by a peduncle, and having the rest of the lower surface covered 

 by concentrically striated and wrinkled epitheca. The thick- 

 ness of the coenosteum varies from less than 2 millim. up to 2-3 

 centim. The surface shows a variable number of low rounded 

 or conical eminences or " mamelons," the apices of which 

 are usually perforated, each with a single circular opening 

 representing the axial canal of one of the astrorhizal systems. 

 From the apices of the mamelons radiate more or less con- 

 spicuous astrorhizal gutters, and the general surface is covered 

 with close- set tubercles of various sizes, the smaller of these 

 being imperforate, while the larger ones are perforated at 

 their apices by distinct circular apertures. In places the 

 tubercles coalesce into vermiculate ridges. Parts of the sur- 

 face may be covered with a thin calcareous membrane, per- 

 forated by the apertures of the larger tubercles above spoken 

 of. 



As regards internal structure the skeleton-fibre is minutely 

 porous, and the skeletal tissue is of the incompletely reticu- 

 late type. Vertical sections show well-developed concentric 

 laminffi, each often with a median clear line, the radial pillars 

 being thick and the interlarainar spaces from ^ to j millim. in 

 height. Imperfect zooidal tubes, with few tabulse, are often 

 recognizable. In tangential sections the transversely divided 

 ends of the radial pillars are seen, each often in the form of 

 a ring enclosing a central circular space. It is the free upper 

 ends of these which form the perforated tubercles on the 

 surface. The intervals between the cut ends of the radial 

 pillars are often crossed by delicate partitions, indicating the 

 presence of astrorhizal tabulge, 



Ohs. 8. granulata is the type-species of the genus Stromato- 

 porella, and I have elsewhere figured its minute structure with 

 some fulness (' Monograph Brit, Stromatoporoids,' parti, pi. i. 

 figs. 14, 15, pi. iv. fig. 6, and pi. vii. figs. 5, 6). As I 

 have not repeated these figures here, it is not necessary to 

 discuss the minute characters of the species in greater detail 

 on the present occasion. 8. granulata is undoubtedly very 

 nearly related to 8. eifeliensis^ Nich., but seems to be 

 specifically distinct. As compared with the latter species it 

 is most readily distinguished by the much smaller development 

 of the astrorhizal system, and by the conspicuous presence of 

 liollow radial pillars which appear on the surface as large 



