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
Isca Dumnoniorum ha). There is evidence of copper and bronze working. A possible stock-yard has also been identified and Isca was clearly a key market for livestock, crops, and pottery produced in the surrounding countryside. The importance of Isca as a trading centre is demonstrated by the discovery of more than a thousand Roman coins around the city. However, the dates of these coins suggest that the city was at its most prosperous in the first half of the 4th century; virtually no coins dated after 380 have been found, suggesting a rapid decline. Bishop Ussher identified the Cair listed among the