The map displays only what was known by Richard and his contemporaries, reaching no further than the River Ganges in India, the Nile in Africa and Norway and the Caspian Sea to the North, and for your author one of the most interesting aspects was the strange beasts, creatures and quasi-human animals which lurk around the edges of the map, presumably representing an acute fear of the unknown.
For more, see http://www.herefordcathedral.org/visit-us/mappa-mundi-1