Selenizone
![Four view of the slit shell Mikadotrochus hirasei. The first view shows the selenizone well. The other views show its relationship to the slit in the shell.](/Images/godic/202502/10/Mikadotrochus_hirasei_014121.jpg")
![Three artificially polished shells of a New Zealand abalone, a Haliotis species, probably H. iris. The central shell clearly shows the selenizone as a series of holes](/Images/godic/202502/10/Paua34121.jpg")
A selenizone (from the Greek "selene" meaning "moon", and "zone" meaning "girdle") is an anatomical structure that exists in the shells of some families of living sea snails: the slit shells, the little slit shells and the abalones, which are marine gastropod mollusks from ancient lineages.