It has usually been held that the shield emblems in the Notitia Dignitatum (Not. Dig.) were based upon an official pictorial register or pattern book, containing the unit emblems of the late Roman army. Thought to have been based upon an official source, as the text was, the shield emblems of the Not. Dig. are imagined to have been accurate in the original manuscript. It was only later, according to this view, that errors crept in during the transmission of the text and illustrations, so that the emblems now appear to be somewhat debased. For example, it is held that some of them no longer accompany the titles for which they were apparently intended.Shifts in the relationship between the emblems and titles have long been noted. But there are other, more fundamental, inconsistencies that have escaped the attention of scholars. These previously led me to raise doubts about the truth of the conventional view above and to entertain the possibility ‘that the artist's sources were so impoverished that he was reduced to relying upon his own powers of invention’. I should now like to explain in greater detail my reasons for rejecting the conventional view and advancing the alternative explanation that the shield emblems of the Not. Dig. were largely ad hoc fabrications. The consequences for our understanding of the Not. Dig. and of the art of the later Roman Empire are obviously considerable.