large numbers of Bositra buchi. These bivalves may have been able to swim freely, thus able to avoid the soupy mud on the sea floor. A limestone known as Fuller's Earth rock is found in the north-west of the county, between the clays south and east of Sherborne. It is rich in ammonites and bivalves. Previously referred to as the Upper Fuller's Earth Clay, the succeeding Frome Clay can be seen to the west of West Bay, where it forms the major part of the West Cliff. It contains many brachiopods, particularly in the Weymouth Anticline where the oyster beds are 5 m thick. At the junction between the Frome Clay and the overlying Forest Marble is the Boueti Bed, so called because of the large numbers of the brachiopod Goniorhynchia boueti found there. It is best viewed on the Herbury peninsula south of Langton Herring. The limestone known as Forest Marble is not a true metamorphic marble but it takes a high polish, and has been used as a building material and marble substitute for many years. Outcrops of Forest Marble are concentrated around the Weymouth Anticline, the coastal escarpment between Burton Bradstock and Abbotsbury, and inland as far as Bothenhampton, where they disappear below younger Cretaceous deposits. Surfacing once more at Rampisham, they turn east and then north into Somerset. The limestone does not form one continuous bed as previously thought, but rather forms pockets in a formation that is predominately clay. Severe tropical storms likely swept up large quantities of shells and other invertebrates and deposited them in this way. The formation of the Forest Marble suggests a shallowing of the sea and the remains of pieces of tree, and bits of land-dwelling animals, are found among the turtles, frogs, and salamanders within. Above the Forest Marble lies the Cornbrash sequence of early Callovian age, which is dominated by rubbly limestone. Unsuitable for building stone, these limestones have been used for lime production and road construction. In the north of the county, an already lithified Cornbrash floor was being eroded, and the resulting pebbles gathered serpulid worms, bryozoans, and bivalves as they rolled around beneath the shallow sea. Ancholme Group From the early Callovian to the early Kimmeridgian, the future Dorset, at 36°N, still had a tropical climate and the limestones, clays, silts, and sands from this period were laid down in a marine environment that ranged