Marriages between humans and non-humans (irui konin tan (異類婚姻譚, "tales of heterotype marriages")) comprise a major category or motif in Japanese folklore. Japanese heterotype examples such as the crane story describes a sustained period of married life between the interspecies couple, in contrast to Western examples like Frog Prince or the Leda myth where the supernatural encounter is brief. An unusual pairing occurs in the story of the Hamaguri nyōbo [ja] (蛤女房, "clam wife"), which exist in both a politer written version (otogi-zōshi) and in a more rustic and vulgar oral tale.