Three octagonal steps lead to the socket stone, which is square. The inscription is on the east face. The square shaft seems to be the original one, though the cap and cross are more recent additions. (A photograph of 1896 shows the cross before restoration, with the shaft broken below the capstone, leaving the monument without a cross.)
This cross was erected as a memorial to 315 people who died in Ross during the plague of 1637 and who were buried nearby at night without coffins.
Plague An Dom 1637 Burials 315 Libera Nos Domine
PMSA recording information