There are various insets. One depicting the top of the world, the Arctic region. And one depicting the bottom of the world, the Antarctic region.
If one looks through the map at various points where there may be a blank spot, the mapmaker has chosen to fill them in with some interesting animal life or other activity that characterized that part of the world. Obviously, by this date, not too much was known by the interior either of South America or North America, and when one looks up to the North American portion of the map, there is a great deal of blank space, a great deal of geography yet to be discovered.
For more details, view the catalog record: https://library.villanova.edu/Find/Record/1933458