428 Geological Society. 



tails the steps that led him to infer from zoological evidence alone, 

 that they were of an intermediate age between the Carboniferous 

 and Silurian rocks. 



Mr. John Phillips had already observed the resemblance between 

 many of these Devonian shells and those of the Mountain-limestone, 

 and Mr. De la Beche had long ago noticed the position of the Tor- 

 bay limestones to be incumbent on strata of Old red sandstone ; and 

 in 1839 suggested that their organic remains would seem to indi- 

 cate relations to this formation. The cause of the obscurity that 

 overhung this subject arose partly from the absence of any evidence 

 from superposition, in consequence of the insulated place which 

 these rocks occupied in the south of Devon ; and partly from the 

 non-existence, until a recent period, of any extensive catalogues of 

 the organic remains of the Mountain-limestone and Silurian systems 

 with which these fossils of South Devon might be compared. 



In 1837 Mr. Lonsdale had ascertained, from an extensive colla- 

 tion of the shells and corals of the south of Devon with those of the 

 Silurian system supplied in the catalogue of Mr. Murchison, and 

 of the Carboniferous system in that of Mr. J. Phillips, that a large 

 proportion of the Devonian fossils presented a character interme- 

 diate between those of the formations which lie above and below 

 the Old red sandstone ; and therefore concluded that the strata in 

 which they are found must be subordinate parts of this intermediate 

 formation. The suggestion was adopted by Mr. Murchison and Pro- 

 fessor Sedgwick in 1839, and at once shed forth a new and brilliant 

 light that has rapidly dispelled the darkness in which the slate rocks 

 of this extensive formation had, until this discovery of Mr. Lons- 

 dale, been involved. The first application that was made of this 

 new instrument of identification to the continental rocks led to the 

 immediate solution of the difficulties that had attended the attempts 

 of preceding observers to ascertain the equivalents of the English 

 series in the districts adjacent to the coal-fields of Liege and in the 

 BasBoulonnais; and we have already noticed the vast extent to which, 

 during the past year, a similar identification has been carried in the 

 Rhenish provinces and in Russia. 



We should, however, not forget, that, by the recent examination 

 of Russia, the distribution of fossil animals has been found to be 

 materially connected Avith mineral conditions ; for Mr. Murchison 

 and M. de Verneuil have shown us, that with the resumption of its 

 red and green characters, the vast Old red system of that empire 

 resumes the very same zoological types as in the North of Scotland. 



A short time will probably produce an abundant recognition of 

 the same paltaeozoic classification in America. We have long been 

 learning an instructive lesson as to the comparatively small value of 

 mineral character in determining the age of strata, where tliere is 

 no opportunity of appealing to the test of superposition ; and organic 

 remains have been found to supply the surest and safest criterion 

 whereby formations can in such cases be made out ; thus, the evi- 

 dence of fossil shells has recently enabled us to identify the Oolite 

 formation in Cutch and the deserts adjacent to the Indus, and on the 



