View of the spheres, and the dagger, looking towards the entrance. From: here.
In the white-black mosaic-floor of the central aisle near the entrance there is a
dagger and behind it follow seven half circles (seven spheres of the planets) (MMM
II 245; Paschetto, Ostia, fig. 121; cl. Cumont in CRAI 1945,415; see fig. 72).