In the apse of the Greek-columned interior is a delightful mosaic of St. Apollinaris, Ravenna's first martyr and bishop, surrounded by 12 sheep representing the Apostles, with Moses and Elijah in the clouds above him.
The twelve sheep surrounding St. Apollinaris represent the twelve virtues. 
mnli hypothesis: The twelve sheep surrounding St. Apollinaris represent the twelve virtues.  premise: In the apse of the Greek-columned interior is a delightful mosaic of St. Apollinaris, Ravenna's first martyr and bishop, surrounded by 12 sheep representing the Apostles, with Moses and Elijah in the clouds above him.