Cornovii (Cornwall) Dumnoniorum (present day Exeter), it is likely that he only listed Roman places, not purely native sites. Of these, there has been speculation that Voliba might be a place in Cornwall and Tamara is assumed to be on the River Tamar, the border between Cornwall and Devon. Ptolemy's list is supplemented by the problematical Ravenna Cosmography, which lists sixteen names before Isca Dumnoniorum (which is listed as "scadum namorum", showing some of the problems of this source) and which have therefore been assumed to be west of Exeter. Several have been identified as most likely in Devon, leaving "purocoronavis" (the
Southern England Chalk Formation name of the Western Downs is given. The Downs enclose the rich district of the Weald, where the chalk has eroded to form a much flatter landscape. In Wiltshire is Salisbury Plain, the Wiltshire Downs, and Cranborne Chase, all three famous for their archaeology, and it was on these downs that Augustus Pitt Rivers developed the methods of modern archaeological field work in the 19th century. The Berkshire Downs and White Horse Hills adjoin the northernmost part of this formation. The formation called Cranborne Chase () is a chalk plateau in central southern England, straddling the counties Dorset, Hampshire and