It is a well-known fact that the shell-bearing gravels of the Western counties repose in many localities immediately upon a bed of blue or grey clay. This bed has been described as it appears in Lancashire and Cheshire, by Mr. Binney; and more recently by Professor Hull; in North Wales by Mr. E. D. Darbishire; near Rugby by Mr. Wilson; and in numerous localities by Messrs. Taylor, H. F. Hall, D. Mackintosh, and other contributors to the GEOLOGICAL MAGAZINE, in various papers, all testifying to the great extent and importance of this bed.