408 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 24, 



§ 2. Position of the Fossils. 



The organic remains of the London Clay are distributed in groups 

 marking particular zones. Of these zones we may take as types — 

 Sheppey, Highgate*, Copenhagen-fields and Primrose-hill, and 

 Bognor. In consequence of the debris masking the surface of the 

 Sheppey cliifs, and from the circumstance of the fossils always being 

 sought for amongst the shingle on the beach, where the sea leaves them 

 after washing away the clay, their exact position in these cliffs has 

 not yet been determined. One fact, however, is apparent ; the fossil 

 seeds and fruits, which constitute so peculiar a feature in the organic 

 remains of this locality, are found in the greatest profusion here where 

 the cliffs are capped by the Bagshot sands ; the inference, therefore, 

 is, that this singular flora belongs mainly to some of the highest beds 

 of the London Clay, probably chiefly to the upper 50 to 60 feet. At 

 least, I presume that it may be owing to the absence of these highest 

 beds, which alone are wanting at Southend, that the fossil fruits and 

 seeds are so much scarcer there, though well-preserved specimens of 

 shells and Crustacea, similar to those found at Sheppey, abound. 

 Otherwise there is a general community of species, which induces me 

 to include them in one zone, whilst the position of the beds, as deter- 

 mined in fig. 4, p. 405, shows them to be nearly in the same horizon. 

 The few fossils found at Brentwood (in the railway cutting) and at 

 Egfaam Hill belong to this zone. 



The Highgate fossils belong to a rather lower portion of the 

 London Clay ; they occur chiefly near the level of the road at the 

 Archway in beds of sandy clay, which are about 110 to 130 feet 

 below the outlier of Bagshot sands capping the hill. The faunas of 

 Newnhamf and of Clewet's-green J near Basingstoke agree very 

 closely vdth that of Highgate, whilst the position of the beds is also 

 similar §. There is, however, a greater admixture of some of the 

 forms which prevail in the lower zones. 



The Chalk-farm, Primrose-hill, and Copenhagen-fields fossils form 

 another zone, about 100 feet still lower in the London Clay. The 

 fossils of Kew and Brentford belong to this zone, whilst further 

 westward these beds are probably represented by the fossiliferous 

 beds of Cuffell, near Basingstoke 1| ; but here again there is a greater 

 community of species in the several zones. 



The Harwich and Bognor group of fossils belongs to the lowest 

 part of the London Clay, as do also the fossils of the lower strata at 

 Potter's-bar near Barnet, of Sherfield and Old Basing near Basing- 



* That different beds of the London Clay are characterized by peculiar groups of 

 fossils was a fact first noticed in the neighbourhood of London by Air. AVetherell, 

 in 1836, in an interesting paper published in the Lond. and Edinb. Phil. Mag. 

 vol. ix. He there shows that the Highgate fossils are many of them peculiar to 

 that spot, that the fossils of Primrose-lull and Regent's-park constitute another 

 group on a lower level, and considers that the beds at Islington and west of 

 Heme Bay form a third level. 



t Quart. Journ. Geol. Soc. vol. iii. p. 371. % Ibid. p. 370. 



§ Some fossils found at the railway station of the Crystal Palace indicate the 

 occurrence of these beds near the summit of the Norwood bills. 



II Quart. Journ. Geol. Soc. vol. iii. p. 369. 



