This month’s art exhibition at the Medford Public Library is “Mary Oliveira: On Spot Pond,” featuring original watercolors the artist painted from a kayak on Spot Pond in Stoneham. Each painting represents a memory of time spent on the pond. Oliveira’s work will be on display in the library’s second-floor gallery throughout December during regular library hours. An opening reception with the artist will be held from 4 to 6 p.m. on Friday, December 6.