We are systematically surveying all known and suspected Z Cam-type dwarf novae for classical nova shells . This survey is motivated by the discovery of the largest known classical nova shell , which surrounds the archetypal dwarf nova Z Camelopardalis . The Z Cam shell demonstrates that at least some dwarf novae must have undergone classical nova eruptions in the past , and that at least some classical novae become dwarf novae long after their nova thermonuclear outbursts , in accord with the hibernation scenario of cataclysmic binaries . Here we report the detection of a fragmented ” shell ” , 3 arcmin in diameter , surrounding the dwarf nova AT Cancri . This second discovery demonstrates that nova shells surrounding Z Cam-type dwarf novae can not be very rare . The shell geometry is suggestive of bipolar , conical ejection seen nearly pole-on . A spectrum of the brightest AT Cnc shell knot is similar to that of the ejecta of the classical nova GK Per , and of Z Cam , dominated by [ NII ] emission . Galex FUV imagery reveals a similar-sized , FUV-emitting shell . We determine a distance of 460 pc to AT Cnc , and an upper limit to its ejecta mass of \sim 5 \times 10 ^ { -5 } M _ { \sun } , typical of classical novae .