Zupus is the lava-flooded remains of a lunar crater. It is located on a southwestern reach of the Oceanus Procellarum, to the northwest of Mare Humorum. To the north-northeast is the flooded crater Billy, and some distance to the southeast is Mersenius. A system of faint rilles named the Rimae Zupus lie to the northwest, following a course to the north-northwest towards the mare. (wikipedia entry)