The Central Lowlands comprise three main regions, differing in vegetation and water -flow pattern. Their northern part is comprised, in the east, of the Green River Lowlands and in the west, of the Aramassa Lowlands; these are grasslands with an area of desert separating them. The westward-flowing Aramassa River is joined, near its mouth, by a second major river, the Mentone. Extensive swamps, almost at sea-level, lie about the mouths of these two great rivers and that of a third river, the Marolane.These swamplands, the Great Marshes, are the most extensive in Rockall. The Rockall Mountains and Scarpland Hills separate these lowlands from what is still a heavily forested region, - though nowadays in part cleared for agriculture. Its eastern rivers empty into the Lorraine Channel, while its western rivers enter the sea through the Great Marshes, some of them rising from inland swamps known as the Sherman Fens. The forests are divided by the River Antoman, which flows north from the isolated Antoman Hills to empty, not into the sea, but into the Westerlands Lake on the inner side of the low Yorkland Hills. The southern part of the Central Lowlands is again characterized by grassland, both to east and west, with a forested region between. The Serren Lowlands on the east are separated from the Lorraine Channel by two uplands, the Sickle Hills and Munrovia Moor. The more arid western portion is drained by the west-flowing Werenthin River, which empties into Delisle Bay.