¹⁹Weir, Anthony, and James Jerman. Images of Lust: Sexual Carvings on Medieval Churches. London: B.T. Batsford, 1986. 21.
The authors maintain that "folkloric practices are posterior to the importation of the motifs, and that the important moralising tone of the carvings led not only to the preservation of sheelas but also to a popular misconception that they held magical properties." Barbara Freitag, on the other hand, believes that the sheela-na-gig originates within a folk tradition. (Freitag, Barbara. Sheela-Na-Gigs Unraveling an Enigma. New York: Routledge, 2004. 119.) Weir and Jerman are careful to describe the sheela-na-gig as a sexual, but not an erotic, sculpture, as its grotesque and repulsive nature cannot said to be sexually arousing (p. 11-12).
More than 100 sheela-na-gig figures have been noted in Ireland. (Cherry, Stella. A Guide to Sheela-Na-Gigs. Dublin: National Museum of Ireland, 1992.) The listing from the text is excerpted here.