EEVOLUTIOXS. 89 



As the opinion here advanced is so very different from 

 that which is received by modern authors, it seems neces- 

 sary, before giving the proofs of its truth, to trace those 

 circumstances which have operated in leading into error. 



The shells and corals which are found in a fossil state, 

 have probably been quoted more frequently, as proofs of 

 the truth of the popular opinion on the subject, than any 

 other class of relics. Now, here it may be observed, that 

 for upwards of two centuries past, collections of tropical 

 shells and corals have been forming in this country, and 

 on the continent of Europe. During this period the native 

 productions have been examined and collected by few. It 

 therefore happened, that the tropical testacea and zoophy- 

 tes, were better known than those of temperate regions. 

 An observer, finding a fossil shell or coral, had it not in his 

 power to compare them with the productions of his country, 

 in public collections, or in the descriptions and engravings 

 of books on natural history. He could compare them with 

 the figures or specimens of foreign species only, and if he 

 discovered an agreement in the external appearance of a 

 species, or even a genus, might be led to conclude, that he 

 had found a tropical shell or coral fossil, in Great Britain. 

 A few hasty examinations of this kind, in which remote 

 analogies were suffered to be considered as proofs of iden- 

 tity, and the indications of a genus mistaken for the marks 

 of a species, could not fail to lead the mind to erroneous 

 results. With the progress of science, however, the geo- 

 graphical limits of species and of genera, have been more 

 carefully investigated, collections of native productions have 

 become more numerous and accessible, and the sources of 

 error greatly diminished. It is perhaps necessary to add, 

 that among all those who have attempted to investigate the 

 history of fossil species, there have been very few at tiie 

 same time acquainted with the characters of recent animals, 



