148 



RELICS OF PRIMEVAL LIFE 



M\ I 



surface, in this case resembling very much the 

 appearance of the layer-corals so plentiful in some 

 limestones of later date. 



The external forms of Eozoon are at first sight 

 not very obvious, as they adhere very closely to the 

 containing rock ; but the smaller specimens, when 

 entirely weathered out or disengaged by the solution 

 of the limestone in an acid, usually present the form 

 of a broad inverted cone, like some modern sponges 

 or the broader turbinate fossil corals (Fig. 32). The 

 limestone having, like the other beds of the forma- 

 tion, been much compressed and folded, the speci- 

 mens of Eozoon are sometimes crumpled in these 

 folds or broken across by small cracks or faults, which 

 shilt the laminae slightly out of their places. The 

 cracks thus formed are also sometimes filled with a 

 fibrous variety of serpentine, known to mineralogists 

 as chrysotile and popularly as "rock cotton" or 

 "asbestus." It is finely fibrous, and of a silky 

 lustre, and must have been deposited by water in 

 the cracks and fissures formed by the fracturing of 

 the rock and the contained fossils, by movements 

 taking place after the whole was hardened. Accord- 

 ingly these veins often cross not only the rock, but 

 also the serpentine and calcite layers of the contained 



