Shiz pursued Coriantumr "eastward, even to the borders of the seashore" (Ether 14:26). Thus we might reason that the "plains of Agosh" and "many cities" were not far from an eastern "seashore." We are told that at this location (the borders of the seashore) Coriantumr "gave battle unto Shiz for the space of three days" and so terrible was the destruction on the armies of Shiz that they,
fled to the land of Corihor, and swept off the inhabitants before them, and they pitched their tents in the valley of Corihor, and Coriantumr pitched his tents in the valley of Shurr. Now the valley of Shurr was near the hill Comnor; wherefore Coriantumr did gather his armies together upon the hill Comnor.
From this description we might conclude that from the borders of an eastern seashore, the land of Corihor was just one step in the battle progression. Even if the land of Corihor was directly inland, it was still just a reasonably short distance from the seashore. On the other hand, the battles could have progressed along the borders of the seashore.
According to Warren and Palmer, during the last battles, the mention of a seashore is tied to the eastern seacoast. The lowland area of the Jaredites thus appears to be near the eastern sea, rather than the western sea. Other locations mentioned at that time are the valley of Gilgal, the plains of Heshlon, the wilderness of Akish, the waters of Ripliancum, the hill Comnor, the valley Shurr, the valley of Corihor, the plains of Agosh, and the place called Ogath. The final battle occurred next to a hill they called "Ramah." [Bruce W. Warren and David A. Palmer, The Jaredite Saga, 7-7, unpublished] [See the Geographical Theory Map]