1844.] 389 



4. On the Occurrence of a Bed of Septaria, containing Fresh-water 

 Shells, in the Series of Plastic Clay, at New Cross, Kent. By 

 Henry Warburton, Esq. M. P., F. R. S. 



Having occasion, in the spring of 1843, to travel along the South 

 Eastern Railway, I observed at the distance of about 200 yards 

 to the south of the New Cross Station, on the western side of the 

 cutting which there lays bare the junction of the London and 

 Plastic Clays, and at the very foot of that cutting, what seemed to 

 be a continuous bed of stone, forming a part of the Plastic Clay 

 series. 



I applied, in consequence, to Mr. Simms, a Fellow of our Society, 

 (who, as one of the resident engineers, had ready access to every 

 part of the line), to procure for me specimens of this bed ; and he 

 not only complied with this request, but also made a vertical sec- 

 tion of the beds exposed in the cutting, extending from the base of 

 the London Clay to the bed of stone in question. 



The specimens which Mr. Simms procured contain, imbedded in 

 the substance of the stone, two fresh-water shells, a Paludina and a 

 Unio, which Professor E. Forbes has examined and described. 

 The stone proved, on examination, not to form a continuous stra- 

 tum extending to any distance, but to occur at intervals only ; and 

 to be, in fact, a bed of Septaria, of a texture considerably more 

 earthy than the Septaria of the London clay usually are. These 

 Septaria may be traced along the base of the railway cutting from 

 the point already mentioned, south of the New Cross Station, to 

 beyond the first bridge which crosses the railway south of that 

 station, and rising, like the railway itself, at an inclination of 1 

 in 100. 



The position of this bed of fresh-water Septaria, in relation to the 

 London clay, will be best understood from the following section by 

 Mr. Simms : — 



Ft. In. 



1. London clay, the lowest bed of which, from 10 to 15 feet tliick, is 



of a blue colour. 



2. Rolled flint pebbles -■ 110 



3. Fine fawn-coloured sand - - - - - - - -03 



4. Lignite ..-.--..... o o\ 



5. Fine fawn-coloured sand - - - - - - - -20 



6. Ferruginous sand, with fragments of oyster shells, and Cerithia -04 



7. Grey sand, with fragments of Cerithia - - - - - 8 



8. Strong black clay - - - - - - - - -010 



9. Black clay and sand, with fragments of oysters and Cerithia -09 



10. Black sand -- 04 



1 1 . Dark sand, with oyster shells - - - - - - -06 



7 6i 



12. Calcareous stone, with fresh- water shells - - - - -06 



13. Sand and stone in a rotten state, with oysters - - - C- 3 



8 Si 



G G 2 



