Austeravia

Dictionary of Greek and Roman Geography

AUSTERA´VIA or AUSTRA´NIA, the German name of an island in the German Ocean (probably Ameland), signifying the sister island.The Romans called it Glessaria, because their soldiers are said to have found amber (glessumor glass) there. (Plin. Nat. 4.27, 37.11.2.)
[L.S]