INADEQUATE EVIDENCE OF SYNCHRONISM. 333 



occur in America ; and this, notwithstanding the wide 

 range which the Anthozoa are known to have. Similarly 

 of the Mollusca and Crinoidea, it appears that, while then 

 are sundry genera found in America that are found here, 

 there are scarcely any of the same speciesi And Sir 

 Charles Lyell admits that &quot; the difficulty of deciding on 

 the exact parallelism of the New York subdivisions, as 

 above enumerated, with the members of the European 

 Devonian, is very great, so few are the species in common.&quot; 

 Yet it is on the strength of community of fossils, that the 

 whole Devonian series of the United States is assumed to 

 be contemporaneous with the whole Devonian scries of 

 England. And it is partly on the ground that the Devo 

 nian of the United States corresponds in time with our De 

 vonian, that Sir Charles Lyell concludes the superjacent 

 coal-measures of the two countries to be of the same age. 

 Is it not, then, as w r e said, that the evidence in these cases 

 is very suspicious ? 



Should it be replied, as it may fairly be, that this cor 

 respondence from which the synchronism of distant forma 

 tions is inferred, is not a correspondence between particu 

 lar species or particular genera, but between the general 

 characters of the contained assemblages of fossils between 

 \\\e fades of the two Faunas; the rejoinder is, that though 

 such correspondence is a stronger evidence of synchronism 

 it is still an insufficient one. To infer synchronism from 

 such correspondence, involves the postulate that through 

 out each geologic era there has habitually existed a recog 

 nizable similarity between the groups of organic forms in 

 habiting all the different parts of the Earth ; and that the 

 causes which have in one part of the Earth changed the or 

 ganic forms into those which characterize the next era, have 

 simultaneously acted in all other parts of the Earth, in such 

 ways as to produce parallel changes of their organic forms. 

 Now this is not only a large assumption to make ; but it is 



