mottled, sands showing no distinct lines of bedding, and containing few traces of organic remains. Mr. Prestwich states that the well-known blocks of light-coloured, or marly white, saccharine sandstone are met with chiefly in the upper beds of these sands, generally just below the Drift gravel. They are found by sounding the sands and gravel with iron rods. Some of these concretions attain a size of 10 to 12 feet across, and are 3 to 4 feet in thickness. Flint-pebbles, sometimes only slightly rolled and angular, at other times perfectly rounded, occur in them. The sandstone is friable when first excavated, but hardens by exposure. The Upper Bagshot Beds attain a thickness of from 250 to 300 feet. They are best exhibited on Frimley and Chobham Ridges, which are formed entirely of them, and in the heaths of Bagshot, Hartford Bridge, and Sandhurst. Their thickness in the Isle of Wight is estimated by Mr. Bristow at from 140 to 200 feet: here they are of considerable economic value, on account of their whiteness and purity, which render them particularly suitable for making glass, for which purpose they have been extensively worked for many years. Being developed at Headon Hill, they have been known as the Headon Hill Sands. UPPER EOCENE OR FLUVIO-MARINE SERIES. The term Fluvio-Marine Series has been applied to the Headon, Osborne, Bembridge, and Hempstead Beds, because they are partly of freshwater and partly of estuarine or marine origin. They are most completely developed in the Isle of Wight, where their relations and palæontological contents were systematically worked out by Edward Forbes. No members of the series are met with in the London Basin. T These beds, named from their occurrence at Headon Hill in the Isle of Wight, consist of green shelly sands and limestones, which were subdivided by Prof. Forbes as follows:- 2 Upper Uppermost marls with Cerithium lapidum, and Upper Headon Headon freshwater and brackish beds, and sands with Potamomya. Middle Headon,3 with Cytherea incrassata (Venus Bed), and Neritina conrava (Neritina Bed). Lower Headon,' fresh- and brackish-water beds, in which Cyrena cycladiformis is a marked shell. Thickness, 67 feet at Headon, and 40 feet in Whitecliff Bay. The total thickness of the Headon Beds varies from 133 feet at Headon Hill to 175 feet at Whitecliff Bay. Paludina lenta, Planorbis euomphalus, Limnoa longiscata, Potamides cinctus, Ostrea flabellula, and Chara Wrightii, are the most abundant species. At Hordwell Mr. S. V. Wood obtained the Spalacodon (an insectivorous Mammal), also remains of Crocodile, Tortoises, &c. According to Baron von Koenen (1864) railway-cuttings in the New Forest (Brockenhurst, &c.) have exposed certain marine beds overlying the Lower Headon (freshwater) series, and containing fossils hitherto unknown in England, but which he believes to constitute the marine equivalent of the Middle Headon strata. OSBORNE BEDS. These Beds, named by Prof. Forbes after the Royal demesne of Osborne, are subdivided into: 2. St. Helen's Sands. 1. Nettlestone Grits. The Headon and also the Osborne Beds are sometimes placed with the Middle Eocene. 2 The Upper Freshwater formation of Webster. 3 The Upper Marine formation of Webster. 4 The Lower Freshwater formation of Webster. The St. Helen's Sands comprise pale green, yellow, and white sands, hardening into sandstone, with white and yellow marls and clays, having a total thickness of about 80 feet. The Nettlestone Grits, which underlie them, include beds of grit, soft sandstone, clay and limestone, having a thickness of about 20 feet. The sections vary much in detail. They yield Chara Lyelli, Limnoa longiscata, Paludina lenta, Melania excavata, Planorbis, &c. BEMBRIDGE BEDS. This series was subdivided by Prof. Forbes into : : Upper Bembridge Marl, consisting of marls and laminated grey clays, yielding in great abundance Melania turritissima. Lower Bembridge Marl, comprising unfossiliferous mottled clays alternating with fossiliferous laminated clays and marls, with Cerithium mutabile, Cyrena pulchra, &c. Bembridge Oyster Bed, a band containing Ostrea Vectensis. Bembridge Limestone, comprising the uppermost shell-limestones of Headon Hill, Sconce, Hempstead Ledge, Gurnet Bay, Cowes, Binsted, Bembridge, &c. This limestone is sometimes hard and compact, at others soft and tufaceous. It contains Bulimus ellipticus (Bulimus limestone), Helix globosa, Planorbis discus, and Limnæa longiscata (Limnæan limestone). The Bembridge limestone has been largely quarried at Binsted, East Cowes, &c.; but the beds are now seldom worked. The Bembridge Beds have yielded remains of Trionyx; also the Mammalia, Anoplotherium, Charopotamus, and Palæotherium. HEMPSTEAD BEDS. These beds, deriving their name from their occurrence at Hempstead, were divided by Prof. Forbes into : Corbula Beds, brown and greenish clay with shelly bands, Freshwater Corbula pisum, C. Vectensis, &c. (Upper, containing Cerithium plicatum, C. elegans, Middle, with Cyrena semistriata, Cerithium, These beds have been classed as Lower Miocene by Sir Charles Lyell, as Prof. Heer has recognized among some plant-remains found in them, four species common to the lignite of Bovey Tracey. MIOCENE. Until the year 1857 no traces of Miocene beds were suspected to exist in England; at that time attention was drawn to the lignites of Bovey Tracey in Devonshire; but it was not until 1860 that the question was finally settled. Then through the liberality of Miss Burdett Coutts these lignite-beds were minutely investigated by Mr. Pengelly, and the plant-remains collected under his superintendence were submitted for determination to Dr. Oswald Heer, who pronounced them to be undoubtedly Miocene. Lyell places the beds in the Lower Miocene division, as also the Hempstead Beds. BOVEY BEDS. The celebrated clays and lignite-beds of Bovey Tracey have been long known, for the 'Bovey Coal' has probably been worked for the last 150 years. 1 Sometimes spelt Meiocene. |