SILURIAN FOSSILS. 57 



what geologists call the PALEOZOIC EPOCH. These 

 strata are the Cambrian, the Silurian, the De- 

 vonian, the Carboniferous, and the Permian 

 Formations. 



These various groups also we shall notice in 

 the order of their antiquity, commencing with the 

 most ancient, and so advancing upwards towards 

 the secondary and tertiary deposits, and observ- 

 ing as we approach the period when man inhabits 

 the earth, the changes which from one epoch to 

 another take place in the character of the living 

 creatures by which the earth is inhabited. 



I. We first notice therefore the Silurian for- 

 mation, which, so far at least as fossils are con- 

 cerned, may be said to include the Cambrian also. 

 The Silurian, as already described, is largely deve- 

 loped in various parts of England and Scotland, 

 and is in many places bounded by the sea-shores. 



The investigations of geologists have not suc- 

 ceeded in bringing to light any vegetable remains 

 in the Silurian system in Europe, with the ex- 

 ception of some imperfect indications of fucoids 

 or marine plants of the simplest character. The 

 lowest Silurian deposits in which those fucoids 

 appear, rest upon the primitive crystalline rocks 

 which contain no fossils, and it has been assumed, 

 therefore, that they indicate the first indications 

 of organic creation. But this view is not held by 

 Lyell, who states in his Travels in America, 

 that, although the Silurian strata in Europe con- 

 tain no remains of vegetables except the fucoids, 

 the same strata in America exhibit abundant 



