The Equites Dalmatae Passerentiaci are a unit from the command of the Magister Equitum in Gaul. On his Notitia site Luke Ueda-Sarson suggests that Passerentiaci refers to a place, perhaps Passaro in Epirus - it might just possibly be a nickname "sparrows." Shaun Watson (Redzed) painted these for me, lovely jobs, except I hand-painted the shield designs based on Luke's page.
These chaps will be veteran light cavalry with javelin in TtS! terms and will likely get their first outing at Partizan in two weeks, when I am planning a big Late Roman game with various chums.