imperfectly-hnown Sjjecies of Stromatoj)oroids. 231 



fibre from its normal porous condition is well figured bj von 

 Eosen {he. ci't. pi. i. fig. 2) in a vertical section of S. ti/pica. 

 So close is the resemblance thus caused between vertical 

 sections of ^. astroites and corresponding sections of 8. typica 

 that I was at first led to think that A. astroites would prove 

 to be only a highly altered condition of 8. typica (Mon. Brit. 

 Strom, p. 12). Since examining better-preserved specimens 

 of A. astroites I am, however, satisfied that this view is 

 luitenable, since tangential sections of the two species are quite 

 dissimilar. In any case it need hardly be pointed out that 

 the true A. astroites, Kosen, is quite distinct from the form 

 to which Bargatzky gave this name and which I have here 

 described as A. hehbornense. 



Formation and Locality. Silurian (Upper Oesel group), 

 Kaugatoraa-pank and Hoheneichen, Island of Oesel. The 

 species also seems to be present in the Wenlock Limestone of 

 Gotland and also of Britain (Ironbridge) . 



Actinostroma hifarium, Nich. (PI. VI. figs. 4 and 5.) 



The coenosteum in this species is massive, generally hemi- 

 spherical in shape, and of considerable size. The radial 

 pillars are " continuous " and of two sizes, large and small. 

 The large radial pillars are from ^to^ millim. apart, the small 

 ones are from ^ to -^ millim. apart. All the pillars give out 

 numerous radiating horizontal " arms," which give rise in 

 tangential sections to the characteristic " hexactinellid " struc- 

 ture of all the species of Actinostroma. Vertical sections 

 (PI. VI. fig. 5) show the two kinds of pillars and the " con- 

 centric laminte," the latter being from j to ^ millim. apart. 

 AstrorhizEe are wanting. 



Ohs. This species is of the general type of A. clathratum ; 

 but it difiers from this, as from all other recorded species of 

 the genus, in the possession of two distinct sets of radial 

 pillars of different sizes. The specimens figured are from 

 the Rhenish Devonian rocks ; but the species is apparently 

 more abundant in Devonshire than in Germany. 



Formation and Locality. Middle Devonian, Teignmouth, 

 Devonshn-e (in the pebbles of the Triassic conglomerates) ; 

 also in the Middle Devonian of Bitchel (Paffrath district) . 



Actinost7'oma stellulatum, Nich. (PI. VI. figs. 8 and 9.) 



Coenosteum sometimes laminar, with a basal epitheca, some- 

 times massive, the mass in the latter case being sometimes 

 composed simply of concentrically superposed strata, or being 



