CETRA, or CAETRA (kaitrea, Hesych.), a target, i.e. a small round shield, made of the hide of a quadruped (Isid. Orig. xviii.12; Q. Curt. iii.2). It was also worn by the people of Spain (cetratae Hispaniae cohortes, Caes. B. C. i.39, 48) and Mauritania. By the latter people it was sometimes made from the skin of the elephant (Strab. xvii p828). From these accounts, and from the distinct assertion of Tacitus (Agric. 36) that it was used by the Britons, we may with confidence identify the cetra with the target of the Scottish Highlanders, of which many specimens of considerable antiquity are still in existence. It is seen "covering the left arms" (comp. Virg. Aen. vii.732) of the two accompanying figures, which are copied from a MS. of Prudentius, probably written in this country, and as early as the ninth century (Cod. Cotton. Cleop. c8).

It does not appear that the Romans ever wore the cetra. But Livy compares it to the pelta of the Greeks and Macedonians, which was also a small light shield (cetratos, quos peltastas vocant, xxxi.36) [Pelta].

William Smith, A Dictionary of Greek and Roman Antiquities (London: John Murray, 1875), 269-270.