Geological Society of London. 189 



Bouth-westorn promontories of tlio isliimls of Groat Britain and 

 Ireland. 



DisscussiON. — Mr. David Forbes protostod against the notion that the Devonian 



strata tticmsnlvcs were metalliferous, the veins being of nmch later date, — in the 

 present case Post-carboniferous, lie mnintaincd tliat there was no valid reason for 

 supposing that the veins became unproductive with increased depth, and opposed the 

 notion that they had been filled in by segregation from the surrounding rock, lie 

 alluded to the use of spectroscopic analysis in such in([uiries, and remarked that as no 

 trace of copper is to be found in the rock, even immediately adjacent to veins, we 

 should have to admit, on the hypothesis of segregation, that the rock must originally 

 have contained precisely the amount of metal segregated in the veins. 



Mr. Etheridge agreed with Mr. Forbes as to the date of the filling in of the veins. 

 He also maintained the justice of correlating the rocks with those of the Cornish 

 area. 



Mr. Hyde briefly replied. 



Geological Society of London. — III. Marcli 9th, 1870. — 

 Warington W. Smyth, Esq., F.E.S., Vice-President in the chair. 

 The following communications were read : — 1. " On the structure of 

 a Fern-stem from the Lower Eocene of Heme Bay, and on its allies, 

 recent and fossil." By W. Carruthers, Esq., F.L.S., F.G.S. The 

 author described the characters of the fossil-stem of a Fern obtained 

 by George Dowker, Esq., F.G.S., from the beach at Heme Bay, and 

 stated that in its structure it agreed most closely with the living 

 Osmimda 7-egaUs, and certainly belonged to the Osmundacese. The 

 broken petioles show a single crescentic vascular bundle. The section 

 of the true stem shows a white parenchymatous medulla, a narrow 

 vascular cylinder, interrupted by long slender meshes, from which 

 the vascular bundles of the petioles spring, and a parenchymatous 

 cortical layer. The author described the arrangement of these parts 

 in detail, and indicated their agreement with the same parts in 

 Osmunda regalis. He did not venture to refer the Fern, to which 

 this stem had belonged, positively to the genus Osmunda, but pre- 

 ferred describing it as an Osmundites, under the name of 0. Dowlceri. 

 The specimen was silicified, and the author stated that even the 

 starch grains contained in its cells, and the mj'^celium of a parasitic 

 fungus traversing some of them were perfectly represented. Its 

 precise origin was unknown ; it was said to be probably derived 

 from the London Clay, or from the beds immediately below. 



Discussion.— Mr. "W. W. Smyth, in calling on those present for remarks on the 

 paper, commented on the very remarkable manner in which the minutest details of 

 the original plant had become silicified. 



Mr. Etheridge mentioned the discovery of fossil fern-stems of somewhat similar 

 character at Bromsgrove. 



Prof. Ramsay suggested the possibility of the fossil having been derived from a bed 

 even higher than the Thanet Sands. He thought the rarity of such delicate structures 

 being perfectly preserved by silicifi^cation not so great as might at first sight appear, 

 for in Antigua and elsewhere vegetable forms had been converted into flint as com- 

 pletely Hnd distinctly. 



Mr. Woodward cited the hotsprings in the Island of St. Michael as converting 

 portions of vegetables still growing into flint. He had heard, from the agent of 

 Sir Woodbine Parish, of the ends of piles driven into the beds of rivers in Parao-uay 

 and elsewhere in South America having been converted into flint in the course of 

 thirty years, but had not yet seen them. 



Mr. Jenkins inquired whether the Osmundee from different formations offer any 



