298 On the Structure and Position of Eozoon Canadense. 



continuous asbestiform layer covering the segments, long 

 straight bundles of asbestiform filaments radiating from them. 

 What is the import of these — whether they represent a part of 

 the original structure of the animal, or are (as I am disposed 

 to suspect) a product of subsequent metamorphism — is a point 

 which must be reserved for further investigation. The age of 

 the Connemara rock, too, can scarcely be regarded as con- 

 clusively settled. Sir Roderick Murchison, by whom its 

 relations were carefully studied some years ago, seemed not 

 indisposed, when it was first found to contain Eozoon, 

 to believe that it might belong to the Laurentian series ; 

 but he has since withdrawn that admission, and has ex- 

 pressed the opinion that the Connemara marble is of 

 Silurian age.* If this be the case, it proves that Eozoon was 

 not confined to the Laurentian period, but that it had a vast 

 range in time, as well as in geographical distribution; in 

 this respect corresponding to many later forms of Foramini- 

 fera, which have been shown by Messrs. Parker and Rupert 

 Jones to range from the Triassic to the present epoch. 



It is much to be desired that a careful examination should 

 be made of all Serpentine marbles that contain a Calcareous 

 admixture. Such admixture may be at once detected by their 

 effervescence when touched with dilute acid ; and if, on the 

 removal of the lime by continuous maceration in acid, the 

 siliceous residuum should exhibit forms bearing any decided 

 resemblance to either portion of the Uncoloured Plate, the parti- 

 cipation of Eozoon in their original production may be con- 

 fidently inferred. It is specially to be desired that search 

 should be made for it in any limestone beds occurring in the 

 Laurentian rocks of Scandinavia, and in those of Bohemia 

 and Bavaria. 



It is not only, however, in those rocks which exhibit well- 

 preserved representations of the original animal, that we may 

 trace the agency of Eozoon in extracting from the ocean-waters 

 the materials now forming the solid crust of the globe. There 

 can be no reasonable doubt that — as has occurred in many 

 subsequent epochs, and may be shown to be in progress at the 

 present time — there was a continual disintegration, by the 

 mechanical force of the ocean-waters, of those structures 

 which had been built-up by living agency; and that the 

 particles resulting from the progressive wearing-down of the 

 Foraminiferal reefs would be deposited as sediments elsewhere, 

 and, when subjected to subsequent metamorphic action (as by 

 the infiltration of heated water) would be converted into 

 highly crystalline limestones. Sir William Logan has shown 

 me thin sections of solid masses, which presented unmistakable 

 * See the Geological Magazine for April, 1865. 



