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
England–Wales border Insular Celtic languages, and were regarded as Britons. The clear geographical divide between the mountainous western areas of southern Britain and the generally lower-lying areas to the east was reflected in the pattern of Roman occupation. The main Roman military bases for the control of what became Wales were beyond the mountains, at "Deva" (Chester), "Viroconium" (Wroxeter, near Shrewsbury), and "Isca Augusta" (Caerleon, near Newport), all located close to the later national border. When the Roman garrison left around 410, the various parts of Britain were left to govern and defend themselves. The western area, later Wales, had become largely