The recognition by Messrs. Chalupa and Glomb that the "military bag" in the Milesframe of the floor-mosaic of the Mitreo di Felicissimo in Ostia is in fact a butcher's cut is an important correction of detail in that it serves to focus attention upon a theme in the iconography of the Roman cult of Mithras that has been wrongly neglected in favour of supposedly more important "mystery" themes. In the light of the sacrificial scene on the altar of Flavius Aper (Poetovio), the interpretation as a bull's hind-quarter rather than shoulder is to be preferred. The scene at Ostia is perfectly in keeping with other evidence suggesting that (junior) Mithraic grades fulfilled specific manual tasks within the cult, in the case of Miles, butchery of sacrificial animals.