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 A HISTORY OF BERKSHIRE Corals are abundantly found in the topmost beds, and Messrs. Blake and Hudleston, in their account of the quarry at Bradley farm north of Marcham, describe those beds as ' about six feet of magnificent coral, the massive portions growing in lenticular masses with bases not horizontal and the intermediate spaces filled to a large extent with Thecosmiliae, and they add that the reef corals there are in a more perfect state of preservation than in any locality they know of.' 1 Brachiopoda and bryozoa are not common in this district, and echinoderms are far less abundant than in the Corallian of Calne and other places. As in the Lower Corallian, there are in some of the beds numerous pebbles of quartz, lydite, etc., and there are also rolled fragments of hard limestone bored by Lithodomi and encrusted with Serpulas. The fossils of the Corallian are all marine, and the above evidence points to a sea with shallow sand and coral banks or shoals. The pebbles suggest that land was at no great distance. The late Mr. J. H. Blake stated that good supplies of water are frequently to be obtained from the Corallian, but the amount varies according to the circumstances of the locality. Sometimes it is met with in the upper part of the formation being held up by clay seams or chert bands but it is usually most abundant near the bottom, where it is held up by the Oxford Clay. 2 KIMERIDGE CLAY The calcareous beds of the Corallian are overlain by another clayey series, the Kimeridge Clay, which like the older formations already described forms a narrow east and west band across the country. The town of Abingdon stands on it. It is a good deal hidden by gravel and alluvium. It consists of dark-coloured clays and shales with septaria, and occa- sionally nodules or bands of earthy, fossiliferous limestone. The bones of the reptiles Campfosaurus, Ichthyosaurus and Pliosaurus have been found in it as well as many marine shells. Ammonites biplex is characteristic of the upper part and Exogyra virgula and Ostrea deltoidea of the lower. Many other fossils occur and also driftwood. These fossils taken together with the character of the strata show that it is a marine mud accumulated at some distance from land and probably in fairly deep water. Possibly there was land in the west, Cornwall, Wales, etc., and Mr. H. B. Woodward suggests that there was a coast to the south, south-east and east. In Dorsetshire bituminous shales occur in this formation, but have not been recorded in Berkshire. Fruitless trials for coal have been made at times. The soil is cold and stiff. Oaks grow well on it. It is according to Mr. J. H. Blake apparently 140 feet thick at Denchworth, 1 1 1 feet at Goosey, 94 feet at Wantage, and less at Chawley. 1 Quart. Journ. Geol. Soc. (1877), xxxiii. 307. 'The Water Supply of Berkshire from Underground Sources,' Gecl. Survey (1902). 6