upper Volgian of Russia. Contemporaneous rocks are also present in the neighbourhood of Boulogne-sur-Mer, where they are characterized by thin limestones with Cyrena and gypsiferous marls. These French outcrops occur, just like those in England, in the core of the Weald-Artois anticline. Purbeckian aged deposits occur even further south in the Charente. In north-west Germany three subdivisions are recognized in strata of the same age: in descending order Purbeck Kalk, Serpulit and Münder Mergel. Subdivisions Modern The Purbeck Group in Dorset is now divided into three formations, the Lulworth Formation and the overlying Durlston Formation in the south (in the Vectian or Wessex Basin). A third underlying formation, the Haddenham Formation, is identified in Wiltshire, Oxfordshire and Buckinghamshire. Within the Vectian Basin, the Durlston Formation is further divided into a lower 'Stair Hole Member' and an upper 'Peveril Point Member'. Similarly the Lulworth Formation is divided in Dorset into a lower 'Mupe Member', a middle 'Ridgeway Member' and an upper 'Worbarrow Tout Member'. In East Sussex the Purbeck Group is formally subdivided into the Blues and Greys Limestones members Traditional The sequence was traditionally divided into three, though along different lines viz. Upper, Middle and Lower. The Upper Purbeck comprises . of fresh-water clays and shales with limestones, the Purbeck marble and Unio-bed, in the lower part. The Middle division (), mainly thin limestones with shaly partings, contains the principal building stones of the Swanage district; near the base of this subdivision there is a , bed from which an interesting suite of mammalian remains has been obtained; in this portion of the Purbeck Group there are some marine bands. The Lower Purbeck consists of fresh-water and terrestrial deposits, marls, and limestones (the famous Portland limestone) with several fossil soils known as dirt beds. This division is very extensively exposed on the Isle of Portland, where many of the individual beds are known by distinctive names. The chief building stones of Upwey belong to this part of the Purbeck Group. Fossil content No zonal fossil has been recognized for the British Purbeckian strata, but the horizon is approximately equivalent to that of Pensphinctes transilorius of the European continent. The Purbeckian equivalents of Spilsby and Speeton are in the zone of Belemnites lateralis. Other marine fossils are Hemicidaris purbeckensis and Ostrea distonta, the latter being abundant in the Cinder bed of the Middle Purbeck. The fresh-water mollusca include Viviparus (Paludina), Planorbis,