Note 50 — THE AUXILIA DURING THE FIRST TWO CENTURIES A.D.
Reading edition
Arrian, Tactica, 18 αἱ δὲ δύο ταραντιναρχίαι ἱππαρχία, δώδεκα καὶ πεντακοσίων ἱππέων, ἥντινα Ῥωμαῖοι ἴλην καλοῦσιν. It is perhaps worth noting that Vegetius (ii. 14) gives 32 as the strength of a turma of his equites legionis.