A great inland sea lying between Arabia and Persia, and entered from the Indian Ocean through the Gulf of Oman; is 650 m. long and from 50 to 250 m. broad. The Arabian coast is low and sandy, the Persian high. The chief islands are in the W., where also is the Great Pearl Bank. The only river of importance received is the Shat-el-Arab, which brings down the waters of the Euphrates and the Tigris.