The headword probably refers to the Italian city of Florentia, nowadays Florence/Firenze, in Tuscany: Barrington Atlas map 42 grid A1. There was, though, another city of this name on the Danube in present-day Hungary: Barrington Atlas map 20 grid F3.
See also ps.-Zonaras (Tittmann) 1814.19.
[1] The proper name belongs to -- among other early Christian-church figures -- a bishop of Vienna, Gaul (present-day Vienne, Isère, France; Barrington Atlas map 17 grid D2), exiled and executed in ca. 250 CE for his beliefs (Benedictine Monks, p. 114). ps.-Zonaras reports the name at 1813.20, as does ps.-Herodian, Partitiones 146. Adler also cites Ambrosian Lexicon 375.