204 RELICS OF PRIMEVAL LIFE 



extremely thin laminae, closely placed together and 

 very massive, and with little supplemental skeleton. 

 This may be allied to the last, and may be named 

 variety " minora ^ 



All this, however, has nothing to do with the layers 

 of fragments of Eozoon which are scattered through 

 the Laurentian limestones. In these the fossil is 

 sometimes preserved in the ordinary manner, with its 

 cavities filled with serpentine, and the thicker parts of 

 the skeleton having their canals filled with this sub- 

 stance. In this case the chambers may have been 

 occupied with serpentine before it was broken up. 

 At St. Pierre there are distinct layers of this kind, 

 from half an inch to several inches in thickness, 

 regularly interstratified with the ordinary limestone. 

 In other layers no serpentine occurs, but the inter- 

 stices of the fragments are filled with crystalline 

 dolomite or magnesian limestone, which has also 

 penetrated the canals ; and there are indications, 

 though less manifest, that some at least of the 

 layers of pure limestone are composed of fragmental 

 Eozoon. In the Laurentian limestone of Wentworth, 



^ Annals and Magazine of Natural History ^ Sen 4, vol. xiii. 

 P- 457. 



