146 BRITISH STROMATOPOROIDS. 



(" Introduction," p. 12) led to think that A. astroites would turn out to be only a 

 highly altered condition of 8. typica. The examination, however, of well-preserved 

 specimens of A. astroites has shown that this conjecture is quite unfounded. 



The Devonian Stromatoporoid described by Bargatzky as Stromatopora astroites, 

 Rosen, I have previously shown to be a distinct species of Actino stroma, to which 

 I have given the name of A. hebborneuse. 



Distribution. — Actinostroma astroites is only known as occurring in the Silurian 

 Rocks. Von Rosen's original specimens are from Kaugatoma Pank in the Island 

 of Oesel, and I have collected precisely similar specimens in the same formation 

 (Upper Oesel Group) at the same locality, and also at Hoheneichen. The species 

 also occurs at Kattentack in Esthonia, in the zone of Pentamerus esthonus. In 

 the Wenlock Limestone of Wisby, in Gotland, the species seems to be not 

 uncommon, but all the examples I have seen are highly altered. In Britain, A. 

 astroites is only known as occurring in the Wenlock Limestone, and I have 

 collected examples of it at Ironbridge and at Much Wenlock. In the latter 

 locality it is not rare, and is often in a state of excellent preservation. 



■8. Actinostroma fenestratum, n. sp. PI. XVII, figs. 8 and 9. 



The ccenosteum in this species is apparently massive, but the mode of growth, 

 general form, and superficial characters are entirely unknown. Well developed 

 astrorhizEe are sometimes present, but in other examples do not appear to be 

 developed, or, at any rate, are not conspicuous. 



As regards internal structure, the ccenosteum is composed of remarkably stout 

 and strong radial pillars, which appear to run without a break for indefinite 

 distances. About three pillars occupy the space of 1 mm. Not only are the 

 pillars exceptionally thick, but they generally show large axial canals traversing 

 their substance, these canals appearing as dark dots (Plate XVII, fig. 8) or as 

 clear spaces, in tangential sections. The concentric laminse are thick, and some- 

 what irregularly developed, about four interlaminar spaces occupying the space of 

 1 mm. The connecting-processes or " arms " given out by the pillars are stout 

 and few in number, and the " hexactinellid " network shown by tangential sections 

 (Plate XVII, fig. 8) is, therefore, coarse and irregular. 



Obs. — The few examples of this species which I have examined are all from the 

 pebbles of Devonian Limestone in the Triassic conglomerates of South Devon, and 

 are all comparatively small. I am, therefore, unable to give any particulars as to 

 the general form and mode of growth of the species. Moreover, they have all 

 undergone extensive crystallisation and distortion by pressure, so that their 



