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 GEOLOGY They are quite unwaterworn, and appear to have lived on the spot attached to the pebbles which form part of the gravel. They all belong to the group of Calci sponges, that is to sponges whose skeleton spicules are formed of carbonate of lime. Calci sponges are rare fossils in any case, and it is most unusual to find them as here with no admixture of sponges whose spicules are siliceous. About seventeen species occur, the commonest of which, Rapbi- donema faringdonensis, is locally known as the petrified salt cellar. 1 Pebbles of quartz and other rocks are fairly abundant, and amongst them are many fossils derived from oolitic formations. Thus the Kime- ridge Clay has furnished Exogyra, Ostrea, Perna and Belemnites. There are Cidaris, Diadema, Exogyra and Pecten from the Corallian, and Grypbcea, Belemnites and Ammonites from the Oxford Clay, showing that all these formations were undergoing much denudation during the deposit of the Lower Greensand. Owing to the unconformable overlap of this formation the sponge gravel rests partly on Kimeridge Clay and partly on Corallian beds. Possibly it thins out to the south-east. Mr. Austen remarks 2 that 'apart from the organic remains [this gravel] might be taken for a mass of stratified drift, a geologist who should be guided by such characters as those of general aspect, mineral composi- tion and mode of accumulation, and who, finding himself in one of these pits was required to determine the age of the deposit, might most excusably suppose himself to be in the Crag district of Suffolk : in both accumulations there is a like condition of the mineral materials, a like arrangement of the component beds, and a like proportion, as well as condition, of the included animal remains. In these latter respects the Faringdon Beds are of great interest as they present to us the only instance now remaining in any part of Great Britain of a bank of sub- angular sea gravel of the secondary period.' s The red gravel which rests on top of the sponge gravel at Little Coxwell consists of ferruginous sands and pebbles with beds of hard con- glomerate with Terebratula, bryozoa, etc., but with few sponges. Its thickness is about 20 feet. The highest division of sands, with ironstone and some chert, about 30 feet in thickness, occupies the upper part of Furze Hill, etc., and the ironstone has been worked in former times. These old workings are known as Coles' pits, and one of them is, according to local tradition, the site of the castle of King Cole. 4 Like the underlying beds the bands of iron ore contain marine shells such as Leda, and this is of some 1 See G. J. Hinde and H. B. Woodward, Proc. Geol. Assoc. (1891-2), xii. 327, and references given at p. 333 ; see also E. C. Davey, Papers contributed to the second volume of transactions of the Newbury District Field Club (Wantage, 1874). 2 Loc. cit. p. 454. 3 On November 7, 1 809, Mr. James Sowerby gave a short account of this gravel to the Linnxan Society (Trans. Linn. Sac. x. 405). 4 Davey, op. cit. p. 17. I 9 "2