Dictionary

Mount of the valley

Easton's Dictionary

(Josh. 13:19), a district in the east of Jordan, in the territory of Reuben. The “valley” here was probably the Ghor or valley of the Jordan, and hence the “mount” would be the hilly region in the north end of the Dead Sea. (See ZARETH-SHAHAR.)

International Standard Bible Encyclopedia

Zereth-shahar is said to be situated in or on the "mount of the valley" (behar ha`emeq (Jos 13:19)). Cheyne (EB, under the word) says "i.e. on one of the mountains East of the Jordan valley (compare Josephus 13 27), and not impossibly on that described at length in BJ, VII, vi, 1-3." To the Northwest of this mountain is Wady ec-Cara, wherein there may be a reminiscence of Zereth-shahar. There is no certainty.