GENUS SYRINGOSTROMA. 97 



Genus Syringostboma, Mch. 



(' Palaeontology of Ohio,' vol. ii, p. 251, 1875.) 



Coenosteum massive, formed of successive " latilaminas." Skeleton-fibre 

 minutely porous. The skeletal tissue is, on the whole, of the reticulated type 

 characteristic of the Stromatoporidce, but the radial pillars are distinctly recognisable 

 and some of them may be of large size. Astrorhizse are largely developed. 



I originally founded this genus for a singular Stromatoporoid (8. densum) from 

 the Devonian Rocks of Ohio. My material is unfortunately very limited, but I 

 have recently succeeded in preparing good thin sections, and can therefore speak 

 more confidently as to the real structure of this type. In the minutely porous 

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

 of the skeletal tissue (Plate XI, fig. 13), #. densum quite resembles the species of 

 Stromatopora, Goldf. It has, however, the peculiarity that the coenosteum is 

 traversed at intervals by large- sized radial pillars which are recognisable in both 

 tangential and vertical sections (Plate XI, figs. 13 and 14). I should not have been 

 disposed to regard this feature as of generic value, except that I have recently had 

 the opportunity, through the kindness of Professor J. W. Spencer, of examining 

 an apparently related form which certainly seems worthy of generic distinction. 

 The form in question was described by Professor Spencer from the Upper Silurian 

 formation of New Brunswick (' Bulletin of the Mus. of the Univ. of the State of 

 Missouri,' p. 49, 1884), under the name of Gcenostroma ristigouchense. Tangential 

 and vertical sections of this beautiful type (Plate XI, figs. 11 and 12) show a curious 

 combination of the characters of Stromatopora, Goldf, and Actinostroma, Nich. 

 Thus, the skeleton-fibre has to a marked extent the minutely porous structure 

 which is so characteristic of Stromatopora, properly so called ; while the radial 

 pillars and their connecting-processes are as distinctly and clearly developed as in 

 the type-forms of Actinostroma. The radial pillars, in fact, are exceedingly large, 

 and give off whorls of delicate " arms " or connecting-processes, which are emitted 

 at corresponding levels in a radiating manner, and which circumscribe rounded 

 pores representing the zooidal tubes. The astrorhizal canals are largely developed, 

 and we therefore see in vertical sections (Plate XI, fig. 12), as in similar sections 

 of S. densum, the large rounded apertures which represent the cut ends of these 

 tubes, and upon which the genus Syringostroma was originally based. This 

 latter character is, of course, one of no generic importance, as, indeed, present in 

 all Stromatoporoids with large astrorhizal canals. There can, however, be little 

 hesitation in regarding this type as really distinct from both Stromatopora and 



