THE BRIAN OR DEVONIAN FORESTS. 55 



took for papillae, but now agree with Mr. Thomas in rec- 

 ognising them as minute pores traversing the wall of the 

 disc, and similar to those which Mr. Newton has described 

 in Tasmanite, and which Mr. Wethered has also recog- 

 nised in the similar spores of the Forest of Dean shales. 

 The walls also sometimes show faint indications of con- 

 centric lamination, as if they had been thickened by suc- 

 cessive deposits. 



As seen by transmitted light, and either in front or in 

 profile, the discs are of a rich amber colour, translucent 

 and structureless, except the pores above referred to. 

 The walls are somewhat thick, or from one-tenth to one- 

 twentieth the diameter of the disc in thickness. They 

 never exhibit the triradiate marking seen in spores of Ly- 

 copods, nor any definite point of attachment, though 

 they sometimes show a minute elongated spot which may 

 be of this nature, and they are occasionally seen to have 

 opened by slits on the edge or front, where there would 

 seem to have been a natural line of dehiscence. The in- 

 terior is usually quite vacant or structureless, but in some 

 cases there are curved internal markings which may indi- 

 cate a shrunken lining membrane, or the remains of a 

 prothallus or embryo. Occasionally a fine granular sub- 

 stance appears in the interior, possibly remains of mi- 

 crospores. 



The discs are usually detached and destitute of any 

 envelope, but fragments of flocculent cellular matter are 

 associated with them, and in one specimen from the cor- 

 niferous limestone of Ohio, in Mr. Thomas's collection, I 

 have found a group of eight or more discs partly enclosed 

 in a cellular sac-like membrane of similar character to 

 that enclosing the Brazilian specimens already referred to. 



The characters of all the specimens are essentially 

 similar, and there is a remarkable absence of other organ- 

 isms in the shale. In one instance only, I have observed 

 a somewhat smaller round body with a dark centre or 



