Page:Transactions of the Geological Society, 1st series, vol. 2.djvu/394

384 and animated forest; and from the infinite variety of curvilinear forms in which the branches are found, it is probable that they were possessed of the power of moving their arms in every possible direction, for the purpose of searching for and obtaining their food, which they extracted from the sea-water.

But if we reflect upon the changes which these extraordinary creatures have undergone, our wonder must increase. From some mysterious cause the animal membrane becomes converted into siliceous matter; and we have then to contemplate the idea of their still retaining their original forms and situations but changed into stone. By subsequent convulsions of nature the silicified animals are broken to pieces, whilst the fragments are scattered in all directions. These are enveloped and covered by sand and calcareous matter, the alternate depositions of each with these fossils forming the vast mass of strata we have been examining. Had the animals been overwhelmed by the sand while in their living state, they must have been crushed quite flat by the superincumbent weight; but in no instance is this the case; their cylindrical forms remain perfect, and do not appear to have suffered from pressure.

You will no doubt perceive that in thus supposing the first change of the animal into silex, I have followed the theory of Mr. Parkinson, as stated in his work on organic remains; and the above observations may perhaps tend to confirm the justice of his conclusions. That these fossils contain generally more siliceous matter than the investing stone, appears probable from their greater durability, and indeed in some instances I found them almost wholly siliceous.

Having noticed the extensive distribution of this fossil, I endeavoured to ascertain the several strata in which it is found. In the ferruginous sand, below the green sandstone, I could not find