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 A HISTORY OF NORFOLK for meadow land, is modified by down-washes of sand from the adjacent tracts of Lower Greensand and Drift, The Kimeridge Clay represents a portion of the sea-bed somewhat distant from land, comprising marine mud, which is free from coarse materials, and in which many organic remains have been entombed. Among the more prominent are bone? of large reptiles, such as Pliosaurus^ and of fishes, such as Asteracanthus. Ammonites biplex and the small ovate bivalve known as Lucina minuscula are not uncommon. The characteristic oyster, Ostrea deltoidea, met with in the deep well at Lynn, occurs in the lower part of the formation. Bituminous shale, which may have been caused by the decomposition of animal matter, was met with at Southery. The Kimeridge Clay is not a water-bearing stratum, but it is noteworthy that some supply was met with in a boring at Downham Market, derived probably from stone bands which may have received the rainfall through the covering of Lower Greensand. LOWER GREENSAND A considerable interval of time may have elapsed between the deposition of the Kimeridge Clay and the overlying strata grouped as Lower Greensand, an interval represented elsewhere by the Portland stone and perhaps in part by the Purbeck and Wealden Beds. On this point however we must speak with reserve, as it seems probable from the observations of Mr. G. W. Lamplugh that the basal portions of the Norfolk Lower Greensand may represent in time the Wealden Beds of southern England.* The Lower Greensand comprises a group of sands and ferruginous sandstones locally hardened into Carstone. It is familiar in the brown pebbly sandstone which lies below the Red Chalk in the cliffs at Hunstanton. It is familiar also on the foreshore, where the double system of jointing in the rock has marked the pavement of Carstone into quadrangular masses separated one from another by the erosive action of the sea. Here children delight to disport themselves, jumping from one block to another by the aid of poles. The Lower Greensand stretches southwards beneath the Red Chalk and Gault and the overlying White Chalk, from Hunstanton to Downham Market, with small outlying masses at Southery and Hilgay ; the main outcrop sinking below the fen levels between Downham Market and Stoke Ferry. Where the outcrop is broad and there is an absence of boulder clay, the formation presents a diversified and picturesque tract of sloping ground, broken anon into two minor escarpments and intersected by the waters of the Middleton stream, Nar and Wissey. To the north of Dersingham the formation contains a central clayey portion between two masses of sand and sandstone. The lowermost subdivision is a mass of sharp silvery sands with streaks of fine clay about loo feet thick, known as the Sandringham Sands — beds which take their name from the 4
 * See ' Geology of the Borders of the Wash ' {Geol. Survey), 1899, pp. 16-25.