§ 22. 



ISLE OF SHEPPEY. 233 



Cotton-plant, Bean, Cucumber, Acacia, Pepper, &c* The 

 wood found in the Sheppey clay, is generally in the state of 

 a pyritous lignite, with the ligneous fibres and circles of 

 growth well defined ; it is often veined with brilliant 

 pyrites, and the fissures and cavities are frequently filled 

 with that mineral. It is rarely that any considerable mass 

 of this wood is found free from the ravages of a species of 

 teredo, resembling the recent Teredo navalis, or borer, 

 which inhabits the seas of the West India islands. The 

 shelly tubes sometimes remain, but their cavities, as well 

 as the perforations in the wood, are more or less filled ujj 

 with pyrites, indurated clay, argillaceous limestone, or calca- 

 reous spar ; and specimens, when cut and polished, exhibit 

 interesting sections of these meandering channels. In these 

 specimens, which I collected in 1811, from the cuttings of 

 the canal in the Regent's Park, the structure of the wood, 

 and the form of the shells, are beautifully displayed. f 



22. Bagshot sands and clays. — At Highgate and 

 Hampstead, Purbright and Frimley Heaths, in Surrey, and 

 on Bagshot Heath, extensive beds of siliceous sands, with a 

 middle group of clays and marls occur, but they contain 

 very few traces of organic remains ; the fossils hitherto ob- 

 served are principally casts of shells of Bracklesham species. 

 In cutting through the summit of Goldsworth Hill, four 

 miles north of Guildford, on the line of the London and 

 Southampton railway, teeth and other remains of several 

 genera of fishes were discovered ; the teeth of sharks, and 

 the palates of rays, were the most numerous. Teeth of the 

 saw-fish (Pristis), and of several new genera of cartilagi- 

 nous fishes, were also collected.} 



* See Figures and Descriptions of the Fossil Fruits of the London 

 Clay ; by I. S. Bowerbank, Esq. F.R.S. 



f For a particular account of the Island and its fossils, see " Ex- 

 cursion to the Isle of Sheppey ;" in Medals of Creation, vol. ii. p. 897, 



% See Geology of the Isle of Wight, p. 84. 



