The lotus flower symbolised the Virgin Mary and thus the birth of Christ. The iconography of the lotus as the birth place of Christ ultimately derives from Egyptian mythology with Horus, the young Sun god, being born from a lotus flower. Cf. M. Henig, The Content Cameos, The Ashmolean Museum, Oxford, 1990, p. 101, no. 174 for a similar lotus ring set with a cameo depicting the Christian fish device