Sir R. I. Miu'chison on the Silurian Rocks of Cornwall. 337 



age of the lowest and oldest of the sedimentary rocks of Coin- 

 wall. 



Not having seen the fossils collected by Mr. Peach on the south 

 coast of Coi'nwall, I then found it difficult to come to any other 

 conclusion than that at which Professor Sedgwick and myself 

 had long ago arrived ; viz. that with the exception of the pre- 

 sence, in the north-eastern extremity of the county, of a portion 

 of the culmiferous (carboniferous) trough of central Devon, the 

 remaining and underlying strata of Cornwall -were of the age of 

 the Devonian or Old Red system. The few Cornish fossils which 

 were then shown to me in your museum, were unquestionably 

 similar to those with which I was formerly familiar in Devon- 

 shire and North Cornwall, as well as with those of the Rhenish 

 provinces and the Eifel, which Professor Sedgwick and myself 

 had shown to occupy a like geological position. They were, in 

 fact, forms of the same type as those which, at the suggestion of 

 Mr. Lonsdale and with the assistance of Mr. James Sowerby on 

 one occasion*, and with the help of MM. de Verneuil and 

 d'Archiac on another t, we had published as characteristic of a 

 group of intermediate characters, pertaining to strata lying beneath 

 the carboniferous rocks and above the Silurian system. In a 

 word, they were identical with some of the numerous fossils of 

 Devon and North Cornwall, published in the work of Professor 

 Phillips J J who, in pointing out in certain tracts the connexion 

 of this group with the carboniferous fossils, which he had so well 

 described, and in others with the Silurian forms I had published, 

 had also concluded that the great mass of fossiliferous strata 

 which rise up from beneath the culm measures of central Devon 

 were of the same intermediate characters. In his valuable ]\Iaps 

 of Cornwall and Devon, Sir H. De la Beche gave essentially the 

 same views of geological succession ; and lastly, in his Report 

 upon the geological structure of that region, he described certain 

 detailed sections in the southern districts of Cornwall, to which 

 I will presently advert. 



In proposing the word " Devonian," as applied to the inter- 

 mediate strata in question. Professor Sedgwick and myself for- 

 tunately thus qualified our meaning in regard to the extension 

 of such rocks into Cornwall : — " In asserting that the stratified 

 rocks of Devonshire and Cornwall are, u])on a broad scale, the 

 equivalents of the Carljoniferousand Old Red systems, we do not 

 however deny, tliat in certain tracts tlie loirest members of some 

 of these rocks may re])rescnt the upjyr dirision of the Silurian 

 system ; for although we have as yet found few if any of the 

 fossils most typical of that system, we admit that wlien the sedi- 



• Trans. Geol. .Soc. n. p. vol. v. p. C;5."5. \ Ibid. vol. vi. pp. 221, 30.'J. 



t Pula'ozoic Fossils of Devon and Cornwall. 

 Phil. Mag. S. 3. Vol. 30. No. 202. May 1817. 2 A 



