Kellaway’s rock, which lies just below, so called from a village in Wiltshire, near Chippenham, is a mixture of yellowish and buff sands, with brown and buff sandstone. The chief fossils are Gryphæa Dilatata, and G. bilobata, Belemnites in abundance, and Avicula Braam-buriensis. {95a} The Cornbrash, which succeeds (so called also from a district in Wiltshire, favourable to corn), is a light grey, fine-grained limestone, often so hard as to need blasting. It abounds in fossils. Among them are Avicula Echinata, Ostræa Sowerbyi, Clypeus Ptotii, Ammonites Macrocephalus, A. Herveyi, Nucula Variabilis, Astarte Minima, Trigonia (of four kinds), Modiola (of four kinds), Myacites (five kinds), Cypricardia, Corbicella Bathonica, Pholadomya (two kinds), Cardium (three kinds), Pecten (six kinds), and several more. {95b} The great Oolite (so named from the Greek Oon, an egg, referring to the number of small stones, like fish-ova, found in it) is divided into Oolite clays and O. limestone. The clays are mottled green and bluish, with bands of ironstone, and concretions of lime. They indicate a shallow sea, as contrasted with the Oxford clay. Fossils are not numerous, but Rhinconella Concinna, Gervillia Crassicosta, Modiola Ungulata, Ostræa Gregaria, O. Sowerbvi, O. Subrugulosa, Perna Quardrata, Trigonia Flecta, and Palate of Fish are found. {95c} These beds correspond to the so-called Forest Marble of the South of England. The Oolite limestone beds consist of white soft limestones, having at intervals bands of marly clay. This formation burns well, and makes good lime. Its chief fossils are Serpula, Rhynconella, Terebratula, and T. Intermedia, Avicula Echinata, Corbicella, Lima Rigida, Lucina, Modiola Imbricata, Myacites Calceiformis, Mytilus Furcatus, Ostræa Sowerbyi, Pecten Vagans, Pteroperna plana, Trigonia, T. costata, T. flecta, T. striata, T. undulata. {95d} The Estuarine deposit, underlying the great Oolite limestone, is composed of light blue, green, and purple clays, intersected by soft bands of sandstone, and having at its base a band of nodular ironstone. It is not very fossiliferous, but the following are found:—Rhynconella Concinna, Modiola Imbricata, Ostræa Sowerbyi, Monodonta. {95e} The sandstone bands contain plant-markings in considerable numbers. As its name implies, this formation was produced as the bed of an estuary or tidal river.