i$if PROCEEDINGS OF THE GEOLOGICAL SOCIETY- [Jan. 21, 



It is perhaps worth}^ of notice, that the alteration effected from the 

 original structure of these calcareous fossils, consists merely in the 

 filling up of the cavities of the cells with carbonate of lime, and in 

 the carbonization of their walls. When fragments are exposed to the 

 action of diluted hydrochloric acid, the calcareous matter is removed, 

 and a flexible carbonaceous substance, retaining the form of the 

 fragment, remains. This residual woody matter burns like touch- 

 wood, and leaves a very little white ash. 



Coniferous wood is not unfrequent in the nodules of ironstone, 

 included in the great coal-bed at the Albion mines. After prepa- 

 ring a great number of slices from these nodules, 1 have found them 

 in general to contain wood showing coniferous structure, and in a 

 few instances having the polygonal discs of the cells preserved. More 

 rarely they afford fragments with the structure of Stigmaria. The 

 wood contained in these nodules of ironstone is usually in the form 

 of small rectangular pieces, similar to those which now result from 

 the slow decay of coniferous wood on the surface of the ground ; 

 and it can scarcely be doubted that they are of the same nature 

 with the less perfectly preserved fragments of similar form, which, 

 in the state of mineral charcoal, abound in the surrounding coal. 

 If this view of the nature of the mineral charcoal be correct, we 

 learn from it, that the coal-beds containing these fragments were 

 accumulated under circumstances which permitted the decay of great 

 quantities of the most durable kinds of wood in the open air, and 

 the partial dispersion of their remains. These conditions of decay 

 and accumulation of vegetable matter are at present found only in 

 wooded swamps occasionally overflowed by water. 



3. Stigmaria. — At the extremity of Malagash Point the shore 

 affords a section of rocks of the newer coal-formation, consisting of 

 red and grey sandstone, shale, thin beds of limestone, and a small 

 bed of coal. In one of the beds of shale I discovered a fossil stump 

 of a tree, having connected with it roots with regular scars like Stig- 

 maria. The trunk of the fossil was nearly at right angles with the 

 plane of the containing beds, which are inclined at an angle of about 

 50°*. It was imbedded in coarse dark shale, and rooted in an in- 

 durated clay of the same colour. It was not more than one foot in 

 height, being cut off by a bed of dark laminated shale, with impres- 

 sions of fern leaves. A portion of one of the main roots, ten inches 

 in length, was seen to be attached to the stump, and other portions, 

 whose actual connexion could not be seen, appeared in the surround- 

 ing clay. All of these roots show, more or less distinctly, the 

 regular scars and eccentric pith characteristic of Stigmaria. The 

 whole fossil is a cast in dark indurated clay ; the trunk however 

 shows three well-defined parts. These are, first, an external coaly 

 envelope or bark irregularly corrugated ; secondly, the stony cast, 

 whose surface shows rather indistinct, alternate, smooth and rough 

 vertical stripes ; and thirdly, an eccentric core, probably corre- 

 sponding with that of the roots and having large transverse promi- 



* I saw no other fossils in this bed, only a small part of which was exposed. 



