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 A HISTORY OF WORCESTERSHIRE that the fragments of marine shells at these localities are in some, if not all, cases derived from older Glacial gravels, together with many quartz- ite pebbles and derived Jurassic fossils. In 1836, Murchison, from the evidences afforded by the recent species of mollusca, suggested ' that the sea must at the time have covered the valley of the Severn from Bridgnorth to the Bristol Channel, thus separating Wales and Siluria on one side from England on the other.' ^ Later on the vievv^ of ' The Ancient Straits of Malvern ' formed the theme of an essay by James Buckman.^ Prestwich, in 1892, remarked: 'There can be little doubt that the sea of the Raised Beach period stretched northw^ard up the Valley of the Severn ; but whether it formed a deep bay or estuary, or whether at that time it was prolonged through to the Irish Channel, forming the " Severn Straits " of Murchison, seems uncertain. It is probable that the marine beds at the higher levels should be referred to an earlier stage of the Glacial period.' ^ Mr. W. J. Harrison, however, considers that these recent marine shells were originally derived from a lobe of the ' Irish Sea Glacier ' which invaded Shropshire, and which had scraped up the shells from the bed of the Irish Sea.^ Be this as it may, we can still re- gard those shell-fragments which we find with the mammoth in the valley drifts as having been redistributed from earlier Drift deposits. The district, however, is of considerable interest as being on the borders of the large region which was mantled by the ice-sheet during the accumulation of the Great Chalky Boulder Clay of the midland and eastern counties, and which was not affected by any marked glaciation during the later phases of the Glacial period. The southern limits of the Boulder Clay must be sought to the north of Bredon Hill, the evidences of the ice action being discernible here and there in the Vale of Evesham and in the vale at Aston Magna and Mickleton, where Boulder Clay was observed in 1853 by G. E. Gavey.^ At the time Mr. R. F. Tomes obtained glaciated Chalk from this Drift. In connection with the discovery, it is interesting to note that pebbles of hard red and white Chalk were found by Buckland in 1 82 1, to the south-east of Shipston-on-Stour. ' Modified Drifts,' in the form of thin scattered drifts with quartzite pebbles, and of valley gravels and loams, succeeded the Boulder Clay, or the melting of the ice which brought it ; and these deposits appear to merge into the old alluvial, and, perhaps in part, estuarine deposits of the great Severn Valley. That the Cotteswolds themselves have not been glaciated, is shown by the thick accumulations of oolitic rubble which flank their slopes. ' Proc. Geo/. Soc, vol. ii. p. 334. ^ 8vo, London [1849] > see also W. S. Symonds, The Severn Straits, Svo, Tewkesbury, 1884, and E. Witchell, Prcc. Cotteswold Club, vol. iv. p. 216. ' Quart. Journ. Gecl. Soc, vol. xlviii. p. 287. p. 483 ; and H. B. Woodward, Geo/. Mag. for 1897, p. 485. ^4
 * Proc. Geo/. Aisoc, vol. xv. p. 404.
 * Quart. Journ. Geo/. Soc., vol. ix. p. 29 ; see also S. V. Wood, Jun., ihid. vol. xxxvi.