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GEOLOGY JURASSIC The Lower Lias succeeds the Rhastic without any marked inter- ruption ; locally there may have been some little breaking up of pre- viously formed beds, brought about perhaps by changes of current, but on the whole the Lias came in quietly. The formation occupies much of the southern part of the county. The basement beds consist usually of even-bedded blue limestones and dark shales in thin alternating bands ; certain of the limestones and others which belong to the underlying White Lias contain numerous remains of insects and have long been known through the researches of Brodie as the Insect Beds. Throughout the Warwickshire area the beds are especially rich in species of the lamellibranchs Cardinia and Hippopodium, and the lowest layers abound in the small oyster Osfrea liassica. But it has been found that the ammonites more than any other fossil exhibit a succession of species each of which characterizes a certain part of the formation ; and we thus are enabled to subdivide the Lias into a number of ' zones," of which the lowest is that of Ammonites planorbis. In the district between Evesham and Stratford-on-Avon many sections of the A. planorbis beds have been described, notably by Mr. R. F. Tomes, the Rev. P. B. Brodie and Dr. Wright. At Binton the lowest layer, known as the Guinea Bed (see p. 17), by its peculiar character seems to imply some amount of local interruption in the processes which deposited the lowest limestones and clays of the Lias, which usually follow the Rhastic without any break. At Wilmcote the lowest beds have been extensively quarried and have yielded A. planorbis, A. jo&nsfoni, the crustaceans Glyphea and Eryon and also bones of saurians. The Lower Lias limestones are exposed in the railway cuttings between Stratford-on-Avon and Eatington and were described by Brodie. 1 Near the station north of Upper Eatington, beds characterized by abun- dant specimens of Lima are exposed in a cutting some 60 feet deep ; and at Kineton the cuttings show limestones and shales containing among other fossils A . angu/atus, Gryphaa arcuata and several species of Lima ; the beds here evidently belong to the zone of A. angu/atus, which succeeds that of A. planorbis. At Harbury are extensive lime and cement works in the same zone. In the adjacent railway cutting it appears that the zone of A. planorbis^ usually rich in limestone bands, is represented by about 30 feet of blue clays and shales; 2 the overlying limestones have yielded remains of the saurians Ichthyosaurus and P/esiosaurus, the fish Acrodus, several species of ammonites, including A. bucklandi^ together with lamellibranch shells and crinoids. Beyond Harbury the limestones of the zones of A. angu/atus and A. bucklandi have been wrought at numerous localities towards Rugby. The highest beds of the Lower Lias were formerly well exposed in the railway cutting south of Fenny Compton station, and have been > Quart. Jout-n. Gtol. SK. xxx. (1874), 746. Woodward, op. cit. pp. 159, 160. 19