LOWER SILURIAN FOSSILS. 41 



beds, and the brachiopods, orthis, lingula, and 

 bellerophon, together with orthocerata, these being 

 the first examples of the cephalopoda. And in all 

 rliese cases, the fossils are few and obscure ; they 

 comprise no Crustacea. It is not till we ascend to 

 ii fourth fossiliferous series, Trenton Limestone, 

 that fossils become abundant, or that trilobites 

 iippear. Perhaps even this is not the most de- 

 cisively adverse view which could be derived from 

 the American fossUs, for lately there have been 

 found, in the Green Mountains of Vermont, strata 

 which, from their metamorphic character, are be- 

 lieved by some native geologists to be inferior 

 and of course anterior to the Siliu-ians, and these 

 contain traces of fucoids and of vermiform bodies 

 called Xereites, the last being a humble form of 

 articulata. If this be true, it would at least add 

 materially to the grounds for hesitation before 

 pronouncing definitely, as the Edinburgh reviewer 

 has done, on the commencement of fossiliferous 

 strata and the nature of the first fossils. Here 

 we must also remember, that in rocks of the elder 

 continent anterior to the Silurians, there are lime- 

 stones, held by many to be an indication of or- 

 ganic life at the places where they are found: 

 the chemical experiments of Braconnot upon 



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