Scallop-Shell Apse

Coptic Church
Temple of Hathor, Dendera (plan)

The scallop-shell apse motif is found in many Christian basilicas from Roman times through the Middle Ages and Renaissance. It has been interpreted as a reference to baptism, to Mary as Stella Maris, and many other theories as well. Its use predates Christianity, being found on apsidal elements of pagan Roman baths and fountains, so perhaps the motif was just copied mechanically by early church architects from their pagan predecessors.