290 Bepoet of the State Geologist. 



the Devonian strata of Ohio. The original description contains 

 nothing of generic value. S. densum, however, is said to be 

 composed of concentric laminae of very dense, finely cellulose tis- 

 sue, traversed by numerous horizontal canals. " The upper sur- 

 face exhibits two distinct sets of apertures — firstly, a series of 

 very minute and crowded perforations, which doubtless corre- 

 spond with the cells of the mass ; and, secondly, a larger set of 

 apertures which are very irregularly distributed, and are like- 

 wise very numerous." These are said to be almost certainly the 

 apertures of a series of vertical canals (probably such as fre- 

 quently form the center of astrorhizal systems). The presence 

 of well-marked astrorhizse is also noticed. The figures accom- 

 panying the text appear diagrammatic, and show no new points 

 of structure. 



In the Monograph on British Fossil Stromatoporoids, ISTiohol- 

 SON has brought together his more careful investigations on that 

 group of fossils, and it is to this work that we must look for his 

 latest and best considered results. 



Of the genus Syeingostroma, he gives the following descrip- 

 tion — " Coenosteum massive, formed of successive * latilaminae.' 

 Skeleton-fibre minutely porous. The skeletal tissue is, on the 

 whole, of the reticulated typ echaracteristic of the Stkomato- 

 PORID^, but the radial pillars are distinctly recognizable and some 

 of them are of large size. AstrorhizaB are largely developed.'' 

 He further states, '' In the more minutely porous character of the 

 skeleton-fibre, as also in the essentially reticulate structure of the 

 skeletal tissue, S. densum quite resembles the species of Steomato- 

 POBA, Goldf . It has, however, the peculiarity that the coenosteum. 

 is traversed at intervals by large-sized radial pillars which are 

 recognizable in both tangential and vertical sections. I should 

 not have been disposed to regard this feature as of generic value, 

 except that I have recently had an opportunity, through the 

 kindness of Prof. J. W. Spencer, of examiniug an apparently re- 

 lated form which seems worthy of generic distinction. 



" Tangential and vertical sections of this beautiful type show a 

 curious combination of the characters of Steomatopoea, Goldf., 

 and AcTiNosTEOMA, Nich. Thus, the skeleton-fibre has to a 



