326 Sir R. I. Murchison on the Silurian Rocks of Cornwall, 



Fig. 8. Another still further developed. 56. 



Fig. 9*. Perfect antheridium a ; accessory organ h ; base of the leaf c. 50. 

 Figs, 9 and 10. Longitudinal sections of the sporangium of Psilotum. 50. 

 Fig. 11. Longitudinal section of an antheridium oi Lycopodium denticular 



turn. 400. 

 Fig. 12. Cross section from the sporangium of Psilotum. 400. 

 Figs. 13 — 17. Forms of the development of the s]iores of Psilotum trique- 



trum. 400. 



Plate VL 

 Figs. 1 — 28. Forms of the development of the spores of Psilotum trique- 



trum. 400. 



XXXVI . — On the Discovery of Silurian Rocks in Cornwall. By Sir 

 Roderick Impey Murchison, G.C. St. S.,F.R.S.,V.P.G.S. 

 ^ R. Geogr. S., Honorary Member of the Royal Geological 

 Society of Cornwall, Mem. Imp. Acad. Sc. St. Petersburg, Corr, 

 Roy, Inst. France, ^c. In a Letter addressed to Sir C. Lemon, 

 Bart., M,P., President of the Royal Geological Society of 

 Cornwall, 



My dear Sir Charles, 

 In compliance with the promise I made when attending your 

 last anniversary meeting at Penzance, I now give you a more de- 

 cided opinion than I was then enabled to do, respecting the age 

 of the lowest and oldest of the sedimentary rocks of Cornwall. 



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

 coast of Cornwall, 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 {, 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 



t Trans. Geol. Soc. n. s. vol. v. p. 633. t Ibid. vol. vi. pp. 221, 303. 



