328 Sir U. I. Murchison on the Silurian Rocks of Cornwall. 



whicli Professor Phillips and myself could only venture (so 

 obscure did they appear to us) to give the guarded, though sug- 

 gestive opinion, which Mr. Peach has recorded in your thirtieth 

 Report. I then ventured to surmise, that these ichthyolites 

 might belong to the Upper Silurian rocks, the oldest in which 

 the remains of any vertebrated animals had yet been discovered, 

 because ^'they occurred in rocks forming the axis of South Devon 

 and Cornwall, which I had always considered to be the oldest in 

 that country.'^ 



In pursuing his researches, Mr. Peach published in 1844 a 

 synopsis of the Cornish fossils from various localities, in which, 

 besides the ichthyolites of Polperro, he identified several moUusca 

 from Gorran Haven, Caerhayes, and Carn Gorran Bay, with 

 typical Silurian species. These were the fossils I was so anxious 

 to see at Penzance ; and Mr. Peach having obligingly forwarded 

 them to me in London, I no sooner unpacked the box, than I 

 found that true Silurian and even Lower Silurian rocks existed in 

 Cornwall, — the proofs being the presence of certain simple-plaited 

 Orthida, which are invariably typical of that age. But although 

 Mr. Peach had come to a correct general conclusion, the specific 

 names he attached to the South Cornish fossils in your thirtieth 

 Report are not correct. In respect to the ichthyolites from the slates 

 of Polperro, Pentuan, &c., they have been referred to our mutual 

 friend Sir Philip Egerton, who is better versed in the classifica- 

 tion of Agassiz than any of our countrymen, and he thus writes 

 to me concerning them : — ^^ These remains are very enigmatical, 

 and I cannot identify a single specimen with any form I know. 

 I do not think any one of the fragments belongs either to Ce- 

 phalaspis or Holoptychius. The nearest approach is to Bothrio- 

 lepis. The dorsal fin named by Mr. Peach Onchus Murchisoni 

 (Agass.) is not that species, as far as I can determine from the 

 description of Agassiz, unless it be a more perfect specimen than 

 he has seen. The longitudinal ribs, instead of being uniform 

 (as figured by Agassiz), are notched, more after the manner of 

 Ctenacanthus. The other Onchus may be O. tenuiserratus, but 

 I have not here the means of comparison. From the general 

 appearance of the collection, I should say they difibr from any 

 Old Red or Devonian fishes I have ever seen.^' 



If these ichthyolites do not decisively help us to settle the age 

 of the Polperro zone of rocks, they are still of great interest, as 

 being the only group of fishes worth noticing which has been 

 found in the older rocks of Devonshire and Cornwall*, and also 

 as being associated with shells, which Mr. J. Sowerby identifies 



* Professor Phillips mentions two very imperfect and doubtful scales of 

 fishes, the one in South Devon, the other in North Devon. Palaeozoic Fos- 

 sils, p. 133, figs. 256, 257. 



