London Clay, the chief member of the Lower Eocene (q.v.), is a great marine clay, blue where not in contact with air, but turned to brown for some distance from the surface. It contains layers of septarian nodules, which are collected at Harwich and Sheppey for the manufacture of Roman cement. The clay is about 500 feet thick in the London Basin, and extends from Hungerford (Berks) to Suffolk and the Isle of Thanet, covering most of Hertfordshire, Middlesex, and Essex. In the Hampshire Basin the thinner Bognor clay, and in France the Argile de Dunkerque, are of the same age. The London Clay seems to have been deposited in a bay with a. tropical climate, and water about 100 fathoms deep. Numerous fossil fruits, including those of Nivadiles, allied to Nipa, a palm whose fruits now float down the Ganges, custard-apples, acacias, and Proteaceai, have been found in this clay at Sheppey, together with crabs such as Xanthopsis; many gastropods, including large cowries (Cyprcea), cones, volutes, Fusus and Pleurotoma; Belosepia and six species of Nautilus among cephalopods; Cryptodon (Axinus) angulatum, and other bivalves; rays such as Myliobates, sharks, a sword-fish 8 feet long, and a saw-fish 10 feet long; crocodiles, numerous turtles, and sea-snakes (Palceophis), the earliest known ophidians; birds, including the notched-billed Odontopteryx; and an opossum and the pachyderms Cbryphodon and Hyracotherium. These fossils suggest a comparison between the London area in Lower Eocene time and the shores of the Bay and Sea of Bengal at the present day.