LOWER SILURIAN FOSSILS. 



the only fossils are lingula (a brachiopodous mo! ask) 

 and fucoids. In the next, the Calciferous SandrocL, are 

 fucoidal layers, encrinital beds, and the brachiopods, 

 orthis, lingula, and bellerophon, together with ortho- 

 cerata, these being the first examples of the cephalopoda 

 And in all these cases the fossils are few and obscure ; 

 they comprise no Crustacea. It is not till we ascend to a 

 fourth fossiliferous series, Trenton Limestone, that fossils 

 become abundant, or that trilobites appear. Perhaps 

 even this is not the most decisively adverse view which 

 could be derived from the American fossils, for lately 

 there have been found, in the Green Mountains of Ver- 

 mont, strata which, from their metamorphic character, 

 a* believed by some native geologists to be inferior and 

 a' course anterior to the Silurians, and these contain 

 tra ",es of fucoids and of vermiform bodies called Nereites, 

 the last being an humble form of articulata. If this be 

 true, it would at least add materially to the grounds for 

 hesitation before pronouncing definitely, as the Edin- 

 burgh reviewer has done, on the commencement of fos- 

 siliferous strata and the nature of the first fossils. Here 

 we must also remember, that in rocks of the elder conti- 

 nent anterior to the Silurians, there are limestones, held 

 by many to be an indication of organic life at the places 

 where they are found: the chemical experiments of 

 Braconnot upon masses of these earlier rocks gave am- 

 moniacal and combustible products, likewise indicative 

 of the presence of organic matter : in the same sub- 

 silurian region, " fragments, apparently organic, and 

 resembling cases of infusoria," have been detected,* and 

 in Bohemia actual fossils have been announced. Even 

 dubious traces of life in sub-silurian rocks must be ad- 

 mitted to be of importance, when we consider that they 

 have mostly been subjected to such a degree of heat as 

 could not fail to obliterate organic memorials, seeing that 

 it has even changed the texture of the rocks themselves. 

 From what Mr. Lyellsaw of the Silurian rocks in Ameri- 

 ca, he finds himself called upon, 'in the most emphatic 

 manner, to warn geologists against «« the hasty assump- 

 tion, that in any of these sections we have positively ar- 

 rived at the lowest stratum containing organic remains 

 in the crust of the earthy or have discovered the first living 

 beings which were embedded in sediment." 



* Ansted-s Geology, ii., 60. 



